U.S. patent application number 12/614653 was filed with the patent office on 2010-03-04 for liquid crystal display device and electronic apparatus.
This patent application is currently assigned to SEMICONDUCTOR ENERGY LABORATORY CO., LTD.. Invention is credited to Hajime KIMURA.
Application Number | 20100053519 12/614653 |
Document ID | / |
Family ID | 37450771 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100053519 |
Kind Code |
A1 |
KIMURA; Hajime |
March 4, 2010 |
LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC APPARATUS
Abstract
The present invention provides a liquid crystal display device
including a liquid crystal layer disposed between a first substrate
and a second substrate, a pixel electrode in a reflection region
and a transmission region over the first substrate, a film for
adjusting a cell gap in the reflection region over the first
substrate, and an opposite electrode in the reflection region and
the transmission region over the second substrate. The pixel
electrode in the reflection region is provided over the film and
reflects light. The pixel electrode in the transmission region
transmits light. The pixel electrode in the reflection region and
the transmission region includes a slit. The slit is overlapped
with at least a part of a step portion which is provided by the
film between the reflection region and the transmission region.
Inventors: |
KIMURA; Hajime; (Atsugi,
JP) |
Correspondence
Address: |
ERIC ROBINSON
PMB 955, 21010 SOUTHBANK ST.
POTOMAC FALLS
VA
20165
US
|
Assignee: |
SEMICONDUCTOR ENERGY LABORATORY
CO., LTD.
Atsugi-shi
JP
|
Family ID: |
37450771 |
Appl. No.: |
12/614653 |
Filed: |
November 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11581014 |
Oct 16, 2006 |
7626663 |
|
|
12614653 |
|
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Current U.S.
Class: |
349/114 |
Current CPC
Class: |
G02F 1/133371 20130101;
G02F 2203/09 20130101; G02F 1/133555 20130101; G02F 1/133707
20130101 |
Class at
Publication: |
349/114 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2005 |
JP |
2005-303766 |
Claims
1. A liquid crystal display device comprising: a liquid crystal
layer in a reflection region and a transmission region, interposed
between a first substrate and a second substrate; a film for
adjusting a cell gap in the reflection region, interposed between
the first substrate and the liquid crystal layer; a pixel electrode
in the reflection region and the transmission region, interposed
between the first substrate and the liquid crystal layer; and an
opposite electrode in the reflection region and the transmission
region, interposed between the liquid crystal layer and the second
substrate; wherein: the pixel electrode in the reflection region
and the transmission region includes a slit, the pixel electrode in
the reflection region is provided over the film for adjusting the
cell gap and reflects light, the pixel electrode in the
transmission region transmits light, the slit is overlapped with at
least a part of a step portion which is provided between the
reflection region and the transmission region by the film for
adjusting the cell gap, and the slit is extended radially and
obliquely with respect to one end portion of the pixel
electrode.
2. The liquid crystal display device according to claim 1, wherein
the pixel electrode in the reflection region has an uneven
surface.
3. The liquid crystal display device according to claim 1, wherein
a distance between a boundary portion of the film for adjusting the
cell gap and the pixel electrode in the reflection region is larger
than a distance between a boundary portion of the film for
adjusting the cell gap and the pixel electrode in the transmission
region.
4. The liquid crystal display device according to claim 1, wherein
a width of the slit of the pixel electrode in the reflection region
is larger than that of the slit of the pixel electrode in the
transmission region.
5. The liquid crystal display device according to claim 1, wherein
a width of the slit of the pixel electrode in a boundary portion
between the reflection region and the transmission region is larger
than that of the slit of the pixel electrode in the reflection
region.
6. A liquid crystal display device comprising: a liquid crystal
layer in a reflection region and a transmission region, interposed
between a first substrate and a second substrate; a film for
adjusting a cell gap in the reflection region, interposed between
the first substrate and the liquid crystal layer; a pixel electrode
in the reflection region and the transmission region, interposed
between the first substrate and the liquid crystal layer; and an
opposite electrode in the reflection region and the transmission
region, interposed between the liquid crystal layer and the second
substrate; wherein: the pixel electrode in the reflection region
and the transmission region includes a first slit, the pixel
electrode in the reflection region is provided over the film for
adjusting the cell gap and reflects light, the pixel electrode in
the transmission region transmits light, the first slit is
overlapped with at least a part of a step portion which is provided
between the reflection region and the transmission region by the
film for adjusting the cell gap, the first slit is extended
radially and obliquely with respect to one end portion of the pixel
electrode, and the opposite electrode includes a second slit.
7. The liquid crystal display device according to claim 6, wherein
the pixel electrode in the reflection region has an uneven
surface.
8. The liquid crystal display device according to claim 6, wherein
a distance between a boundary portion of the film for adjusting the
cell gap and the pixel electrode in the reflection region is larger
than a distance between a boundary portion of the film for
adjusting the cell gap and the pixel electrode in the transmission
region.
9. The liquid crystal display device according to claim 6, wherein
a width of the first slit of the pixel electrode in the reflection
region is larger than that of the first slit of the pixel electrode
in the transmission region.
10. The liquid crystal display device according to claim 6, wherein
a width of the first slit of the pixel electrode in a boundary
portion between the reflection region and the transmission region
is larger than that of the first slit of the pixel electrode in the
reflection region.
11. The liquid crystal display device according to claim 6, wherein
a width of the second slit of the opposite electrode in the
reflection region is larger than that of the second slit of the
opposite electrode in the transmission region.
12. A liquid crystal display device comprising: a liquid crystal
layer in a reflection region and a transmission region, interposed
between a first substrate and a second substrate; a film for
adjusting a cell gap in the reflection region, interposed between
the first substrate and the liquid crystal layer; a pixel electrode
in the reflection region and the transmission region, interposed
between the first substrate and the liquid crystal layer; and an
opposite electrode in the reflection region and the transmission
region, interposed between the liquid crystal layer and the second
substrate; and a conductive film in the reflection region
interposed between the first substrate and the film for adjusting
the cell gap; wherein: the pixel electrode in the reflection region
and the transmission region includes a slit, the pixel electrode in
the reflection region is provided over the film for adjusting the
cell gap and transmits light, the pixel electrode in the
transmission region transmits light, the slit is overlapped with at
least a part of a step portion which is provided between the
reflection region and the transmission region by the film for
adjusting the cell gap, the slit is extended radially and obliquely
with respect to one end portion of the pixel electrode, and the
conductive film reflects light.
13. The liquid crystal display device according to claim 12,
wherein the pixel electrode in the reflection region has an uneven
surface.
14. The liquid crystal display device according to claim 12,
wherein a distance between a boundary portion of the film for
adjusting the cell gap and the pixel electrode in the reflection
region is larger than a distance between a boundary portion of the
film for adjusting the cell gap and the pixel electrode in the
transmission region.
15. The liquid crystal display device according to claim 12,
wherein a width of the slit of the pixel electrode in the
reflection region is larger than that of the slit of the pixel
electrode in the transmission region.
16. The liquid crystal display device according to claim 12,
wherein a width of the slit of the pixel electrode in a boundary
portion between the reflection region and the transmission region
is larger than that of the slit of the pixel electrode in the
reflection region.
17. The liquid crystal display device according to claim 12,
wherein the conductive film has an uneven surface.
18. The liquid crystal display device according to claim 12,
wherein the pixel electrode is electrically connected to the
conductive film.
19. The liquid crystal display device according to claim 12,
wherein a distance between a boundary portion of the film for
adjusting the cell gap and the conductive film is smaller than a
distance between a boundary portion of the film for adjusting the
cell gap and the pixel electrode in the reflection region.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid crystal display
device performing a display of reflection type and transmission
type, and particularly to a liquid crystal display device
performing a display of a multi-domain mode.
[0003] 2. Description of the Related Art
[0004] A liquid crystal display device is used for various
electronic products such as a mobile phone, a monitor of navigation
system, and a television. Some of these electronic products are
used outside as well as inside, and a semi-transmission type liquid
crystal display device is known, which includes both features of a
transmission mode and a reflection mode in order to ensure a high
visibility both outside and inside.
[0005] As for a semi-transmission type liquid crystal display
device, a display device is known, which includes a pixel including
a liquid crystal sandwiched between an active matrix substrate and
an opposite substrate, a reflection portion performed a display of
a reflecting mode and a transmission portion performed a display of
a transmission mode (for example, Reference 1: Japanese Published
Patent Application No. 2005-181981).
[0006] This liquid crystal display device includes an interlayer
insulating film for which a thickness of a liquid crystal layer of
the reflection portion is set to be substantially half of a
thickness of a liquid crystal layer of the transmission portion. In
addition, this liquid crystal display device includes an electrode
coating which compensates a difference of work function because of
a connection between a reflecting electrode and a transparent
electrode as an applied voltage adjusting unit in order to
approximate voltages applied to the liquid crystal at the
reflection portion and the transmission portion close to each
other. Further, the reflecting electrode and transparent electrode
are provided with a protruding portion, and the liquid crystal is
formed to have radial gradient orientation.
SUMMARY OF THE INVENTION
[0007] In the case where a liquid crystal is oriented in a radial
gradient manner, there is an advantage that a viewing angle is wide
when displaying an image. However, there are a number of places
where directions of orientation of liquid crystals are different;
there are problems that orientation control of a liquid crystal is
difficult, a defect such as a disclination easily occurs, and image
quality becomes low. In particular, in the case of a pixel
structure combining a reflecting electrode with a transparent
electrode such as a conventional semi-transmission type liquid
crystal display device, there is a problem that these defects are
increased.
[0008] Therefore, the present invention provides a
semi-transmission type liquid crystal display device with high
quality of display by improving a viewing angle when displaying an
image and by suppressing deterioration of image quality due to
disorder of orientation of the liquid crystal.
[0009] One feature of the invention is providing a liquid crystal
display device including a liquid crystal layer sandwiched between
a pair of substrates, which are arranged to oppose to each other,
and formed of a liquid crystal molecule, a reflection region
performing a display of a reflecting mode, a transmission region
performing a display of a transmission mode which are provided over
one of the pair of substrates, and a pixel electrode provided with
a slit portion between the reflection region and the transmission
region. The liquid crystal display device includes a cell gap
adjusting film which is provided in the reflection region so that a
thickness of the liquid crystal layer is substantially half of a
thickness of the liquid crystal layer in the transmission region. A
reflection region of the pixel electrode is formed of a
light-reflecting conductive film (reflection electrode) over the
cell gap adjusting film, and a transmission region thereof is
formed of a transparent conductive film (transparent electrode).
The slit portion is formed along a step portion (or a boundary
portion) which is formed using by the cell gap adjusting film
between the reflection region and the transmission region.
Alternatively, the slit portion is extended radially to an oblique
direction with respect to one end portion of the pixel electrode,
and the step portion (or the boundary portion) which is formed
using by the cell gap adjusting film between the reflection region
and the transmission region is formed along the slit portion.
[0010] Orientation of a liquid crystal of the liquid crystal layer
can be controlled by providing the cell gap adjusting film in the
reflection region performing a display of a reflecting mode, and
overlapping the step portion formed at the boundary portion of the
cell gap adjusting film in accordance with the provision thereof
with the slit portion of the pixel electrode.
[0011] That is, deterioration of image quality due to disorder of
orientation of the liquid crystal can be controlled by using the
boundary portion of the cell gap adjusting film or the step portion
formed accompanying the boundary portion thereof, and the slit
portion to control orientation of the liquid crystal and by
preventing the control from counteracting and interfering with each
other.
[0012] In the aforementioned liquid crystal display device, a
structure of the slit portion can be allowed some modifications.
For example, an end portion on the transmission region side of the
slit portion can be provided apart from the step portion. In
addition, the end portion on the transmission region side of the
slit portion can be located at the inside of a lower edge portion
of the step portion. Further, an end portion of the transmission
region can be provided below the cell gap adjusting film, the end
portion on the transmission region side of the slit portion can be
provided at the inside of a lower edge portion of the step
portion.
[0013] In this manner, even if a structure of the slit portion of
the pixel electrode is changed, orientation of the liquid crystal
of the liquid crystal layer can be controlled by providing the cell
gap adjusting film in the reflection region performed a display of
a reflecting mode, and overlapping the step portion formed at the
boundary portion of the cell gap adjusting film in accordance with
the provision thereof with the slit portion of the pixel
electrode.
[0014] In addition, an upper surface of the cell gap adjusting film
may be an uneven surface, and the light-reflecting conductive film
(reflection electrode) of the reflection region may be formed along
with the uneven surface. By making a surface of the
light-reflecting conductive film (reflection electrode) uneven,
incident light is diffused, so that a whole luminance is averaged
and a clear image can be obtained in the case of displaying as a
reflection type liquid crystal.
[0015] Another feature of the invention is providing a liquid
crystal display device including a liquid crystal layer which is
sandwiched between a pair of substrates, arranged to oppose to each
other, and includes a liquid crystal molecule, a reflection region
performing a display of a reflecting mode and a transmission region
performing a display of a transmission mode which are provided over
one of the pair of substrates, and a pixel electrode provided with
a slit portion between the reflection region and the transmission
region. The liquid crystal display device includes a cell gap
adjusting film which is provided in the reflection region so that a
thickness of the liquid crystal layer is substantially half of a
thickness of the liquid crystal layer in the transmission region. A
reflection region of the pixel electrode is formed of a transparent
conductive film formed over the cell gap adjusting film and a
light-reflecting film formed over a lower layer of the cell gap
adjusting film, and a transmission region thereof is formed of a
transparent conductive film. The slit portion is formed along a
step portion which is formed by using the cell gap adjusting film
between the reflection region and the transmission region.
Alternatively, the slit portion is extended radially to an oblique
direction with respect to one end portion of the pixel electrode,
and the step portion which is formed using by the cell gap
adjusting film between the reflection region and the transmission
region is formed along the slit portion.
[0016] Orientation of a liquid crystal of the liquid crystal layer
can be controlled by providing the cell gap adjusting film in the
reflection region performed a display of a reflecting mode, and
forming a reflection portion including the transparent conductive
film formed over the cell gap adjusting film and the
light-reflecting film formed over the lower layer of the cell gap
adjusting film, and overlapping the step portion of the cell gap
adjusting film in accordance with the provision thereof and the
slit portion of the pixel electrode.
[0017] In the aforementioned liquid crystal display device, a
structure of the slit portion can be allowed some modifications.
For example, an end portion on the transmission region side of the
slit portion can be provided apart from the step portion. In
addition, the end portion on the transmission region side of the
slit portion can be provided at the inside of a lower edge portion
of the step portion. Further, the end portion of the transmission
region can be provided on a lower layer side of the cell gap
adjusting film, and the end portion on the transmission region side
of the slit portion can be provided at the inside of a lower edge
portion of the step portion.
[0018] In this manner, even if a structure of the slit portion of
the pixel electrode is changed, orientation of the liquid crystal
of the liquid crystal layer can be controlled by providing the cell
gap adjusting film in the reflection region performed a display of
a reflecting mode, and overlapping the step portion formed at the
boundary portion of the cell gap adjusting film in accordance with
the provision thereof and the slit portion of the pixel
electrode.
[0019] In addition, a lower surface of the cell gap adjusting film
may be an uneven surface, and a light-reflecting film of the
reflection region may be formed along with the uneven surface. By
making a surface of the light-reflecting film uneven, an incident
light is diffused; therefore, a whole luminance is averaged and a
clear image can be obtained in the case of display as a reflection
type liquid crystal. In that case, disorder of orientation of the
liquid crystal does not happen because an upper surface of the cell
gap adjusting film may be even, by which deterioration of image
quality due to disorder of orientation of the liquid crystal can be
controlled.
[0020] In addition, in the invention, a strip-shaped protruding
portion in an oblique direction with respect to an edge portion of
the pixel electrode is provided with a structure of the
aforementioned liquid crystal display device, and a liquid crystal
display device of so-called multi-domain vertical alignment (MVA)
type can be formed. Such a structure can also be obtained the same
operation effect as described above.
[0021] In accordance with multi-domain, that is, having a plurality
of regions, there is a plurality of directions in which liquid
crystal molecules are inclined, and the ways the liquid crystal
molecules look are averaged even when seen from any direction;
therefore, a characteristic of viewing angle can be improved.
[0022] Note that a strip-shaped slit portion may be provided
instead of the strip-shaped protruding portion in the oblique
direction with respect to the edge portion of the pixel electrode.
In addition, the strip-shaped slit portion may be provided over one
substrate, and the strip-shaped protruding portion may be provided
over the other substrate with the liquid crystal sandwiched
therebetween.
[0023] Another feature of the invention is providing a liquid
crystal display device including a liquid crystal layer disposed
between a first substrate and a second substrate, a pixel electrode
in a reflection region and a transmission region over the first
substrate, a film for adjusting a cell gap in the reflection region
over the first substrate, and an opposite electrode in the
reflection region and the transmission region over the second
substrate. The pixel electrode in the reflection region is provided
over the film and reflects light. The pixel electrode in the
transmission region transmits light. The pixel electrode in the
reflection region and the transmission region includes a slit. The
slit is overlapped with at least a part of a step portion which is
provided by the film between the reflection region and the
transmission region.
[0024] Note that in the invention, being connected is synonymous
with being electrically connected. Therefore, in addition to a
predetermined relation of connection, another element which enables
an electrical connection (for example, a switch, a transistor, a
capacitor, an inductor, a resistor element, a diode, or the like)
may be provided in a structure disclosed by the invention.
Components may be provided without through another element as well,
and being electrically connected includes the case of being
directly connected. Note that an element of various forms may be
used as a switch, such as an electrical switch and a mechanical
switch. That is, any element which can control a flow of current
may be employed, and it is not limited to a specific form of a
switch. For example, a transistor, a diode (a PN diode, a PIN
diode, a schottky diode, a diode-connected transistor, or the
like), or a logic circuit combined therewith may be used. In the
case of using a transistor as a switch, a polarity (conductivity
type) thereof is not specifically limited since the transistor is
operated as a mere switch. However, a transistor with small OFF
current is preferably used. As for a transistor with small OFF
current, a transistor provided with an LDD region, a transistor
with a multi-gate structure, or the like may be used. In addition,
it is preferable to use an n-channel transistor when operating in a
state where a potential of a source electrode of the transistor,
which operates as a switch, is close to a low potential side power
source (Vss, GND, 0V or the like), whereas it is preferable to use
a p-channel transistor when operating in a state where a potential
of a source electrode of the transistor is close to a high
potential side power source (Vdd or the like). This is because it
is easily operated as a switch since an absolute value of a
gate-source voltage thereof can be made to be large. Note that a
CMOS type switch may also be applied by using both n-channel and
p-channel transistors. In the case where a CMOS type switch is
employed, the switch can be operated properly since an output
voltage is easily controlled with respect to various input
voltages.
[0025] Note that a transistor is an element having at least three
terminals including a gate electrode, a drain region, and a source
region. A channel forming region is provided between the drain
region and the source region. Here, it is difficult to precisely
define the source region and the drain region since they depend on
a structure, operating conditions, and the like of the transistor.
Therefore, in the case of explaining a relation of connection of a
transistor, concerning two terminals of the source region and the
drain region, one of electrodes connected to these regions is
referred to as a first electrode, and the other electrode is
referred to as a second electrode, which may be used for
explanation. Note that a transistor may be an element having at
least three terminals including a base, an emitter, and a
collector. Similarly, in this case, the emitter and the collector
may be called a first electrode and a second electrode,
respectively.
[0026] Noted that a structure of a transistor can have various
modes and is not limited to a specific structure. For example, a
multi-gate structure where the number of gates is two or more may
be employed. With a multi-gate structure, an OFF current can be
reduced and reliability can be improved by improving the pressure
resistance of a transistor, and a change of current flowing between
a drain and a source in accordance with a change of voltage between
a drain and a source can be reduced when operating in a saturation
region. Further, gate electrodes may be provided over and under a
channel. By a structure where gate electrodes are provided over and
under a channel, a channel region increases, thereby a current
value is increased, and a subthreshold value (S value) can be
improved since a depletion layer is easily formed. Further, a gate
electrode may be provided over or under the channel. Either a
forward staggered structure or an inversely staggered structure may
be employed. A channel region may be divided into a plurality of
regions, or connected in parallel or in series. Further, a source
electrode or a drain electrode may overlap with a channel (or a
part thereof), thereby preventing a charge from being accumulated
in a part of the channel and operating unstably. Further, an LDD
region may be provided. By providing an LDD region, an OFF current
can be reduced and reliability can be improved by improving the
pressure resistance of a transistor, and a characteristic that a
drain-source current does not change much even when a drain-source
voltage changes when operating in a saturation region can be
obtained.
[0027] Note that a gate includes a gate electrode and a gate wire
(also referred to as a gate line, a gate signal line, or the like)
or a part thereof. Note that a gate electrode corresponds to a part
of a conductive film overlapping with a semiconductor, in which a
channel region is formed, with a gate insulating film sandwiched
therebetween. A gate wire corresponds to a wire for connecting gate
electrodes of pixels and for connecting a gate electrode and
another wire.
[0028] However, there is also a portion which functions both as a
gate electrode and as a gate wire. That is, there is a region which
cannot be specifically distinguished between a gate electrode and a
gate wire. For example, in the case of a channel region overlapping
with a gate wire which is extended, the region functions as a gate
wire and also as a gate electrode. Therefore, such a region may be
referred to as a gate electrode or a gate wire.
[0029] In addition, a region which is formed of the same material
as a gate electrode and connected to the gate electrode may be
called a gate electrode as well. Similarly, a region which is
formed of the same material as a gate wire and connected to the
gate wire may be called a gate wire. In a strict sense, such a
region does not overlap a channel region or does not have a
function to connect to another gate electrode in some cases.
However, there is a region which is formed of the same material as
a gate electrode or a gate wire and connected to the gate electrode
or the gate wire due to a manufacturing margin and the like.
Therefore, such a region may be called a gate electrode or a gate
wire.
[0030] In addition, for example, in a multi-gate transistor, a gate
electrode of one transistor and a gate electrode of another
transistor are often connected with a conductive film formed of the
same material as the gate electrode. Such a region may be called a
gate wire since it is a region for connecting the gate electrodes,
or may be called a gate electrode since a multi-gate transistor can
be considered as one transistor. That is, a component which is
formed of the same material as a gate electrode or a gate wire and
connected to the gate electrode or the gate wire may be called a
gate electrode or a gate wire. Further, for example, a part of a
conductive film which connects a gate electrode and a gate wire may
be called a gate electrode or a gate wire.
[0031] Note that a gate terminal corresponds to a part of a region
of a gate electrode or a region electrically connected to a gate
electrode.
[0032] Note that a source corresponds to a source region, a source
electrode, and a source wire (also referred to as a source line, a
source signal line, or the like), or a part thereof. A source
region corresponds to a semiconductor region which contains a large
amount of a P-type impurity (boron, gallium, or the like) or an
N-type impurity (phosphorus, arsenic, or the like). Therefore, a
region containing a small amount of a P-type impurity or an N-type
impurity, that is, an LDD (Lightly Doped Drain) region is not
included in a source region. A source electrode corresponds to a
conductive layer which is formed of a different material from a
source region and electrically connected to the source region.
However, a source electrode including a source region may be called
a source electrode. A source wire corresponds to a wire for
connecting source electrodes of pixels and for connecting a source
electrode and another wire.
[0033] However, there is a part which functions both as a source
electrode and as a source wire. That is, there is a region which
cannot be specifically distinguished between a source electrode and
a source wire. For example, when there is a source region
overlapping a source wire which is extended, the region functions
both as a source wire and as a source electrode. Therefore, such a
region may be called a source electrode or a source wire.
[0034] Further, a region which is formed of the same material as a
source electrode and connected to the source electrode, or a
connecting portion of the source electrodes may be called a source
electrode as well. A portion overlapping a source region may be
called a source electrode. Similarly, a region which is formed of
the same material as a source wire and connected to the source wire
may be called a source wire. In a strict sense, such a region does
not have a function to connect to another source electrode in some
cases. However, there is a region which is formed of the same
material as a source electrode or a source wire and connected to a
source electrode or a source wire due to a manufacturing margin and
the like. Therefore, such a region may also be called a source
electrode or a source wire.
[0035] In addition, for example, a portion of a conductive film
which connects a source electrode and a source wire may be called a
source electrode or a source wire.
[0036] Note that the same as a source is applied to a drain, and
description thereof is omitted.
[0037] In the specification, pixels may be arranged in matrix.
Here, the case where pixels are arranged in matrix corresponds to
the cases where pixels are arranged in a straight line and a jagged
line in a longitudinal direction or a lateral direction. Therefore,
in the case of performing a full color display with three color
elements (for example, RGB), an arrangement of pixels may include
the case of arranging in stripes and the case where pixels of the
three color elements are arranged in a so-called delta pattern.
Further, a Bayer pattern may be included.
[0038] Note that in the invention one pixel corresponds to one
element which can control brightness. Therefore, for example, one
pixel denotes one color element by which brightness is expressed.
Accordingly, in the case of a color display device formed of color
elements of R (red), G (green), and B (blue), the smallest unit of
an image is formed of three pixels of an R pixel, a G pixel, and a
B pixel. Note that the number of color of color elements is not
limited to three colors and may be formed of more than three colors
such as RGBW (W is white) and RGB to which yellow, cyan, and
magenta are added.
[0039] In addition, as another example, in the case of controlling
the brightness of one color element by using a plurality of
regions, one of the plurality of regions corresponds to one pixel.
However, the case of employing a subpixel is excluded. For example,
in the case of performing an area gray scale display, a plurality
of regions for controlling the brightness are provided for one
color element, which express a gray scale as a whole, and one of
the regions for controlling the brightness corresponds to one
pixel. Therefore, in this case, one color element is formed of a
plurality of pixels. Moreover, in this case, a region which
contributes to a display may differ in size depending on pixels. In
the plurality of pixels forming one color element, a viewing angle
may be expanded by supplying a slightly different signal to each
pixel.
[0040] Note that in the specification, a semiconductor device
corresponds to a device including a circuit which has a
semiconductor element (a transistor, a diode, or the like).
Further, a semiconductor device may be a general device which can
operate by using semiconductor characteristics. A display device
corresponds to a device including a display element (a liquid
crystal element, a light emitting element, or the like). Note that
a display device may be a main body of a display panel in which a
plurality of pixels including a display element such as a liquid
crystal element or an EL element and a peripheral driver circuit
for driving the pixels are formed over a substrate. Further, a
display device may include an element (an IC, a resistor, a
capacitor, an inductor, a transistor, or the like) which is
provided with a flexible printed circuit (FPC) or a printed wiring
board (PWB). A display device may include an optical sheet such as
a polarizing plate or a retardation film. In addition, a backlight
(such as a light conductive plate, a prism sheet, a diffusion
sheet, a reflection sheet, a light source (LED, cold-cathode tube,
or the like) may be included.
[0041] Note that in the display device of the invention various
modes and various display elements can be applied. For example, a
display medium in which contrast is changed by an electromagnetic
effect can be used, such as an EL element (an organic EL element,
an inorganic EL element, or an EL element containing an organic
material and an inorganic material), an electron-emissive element,
electronic ink, a grating light valve (GLV), a plasma display
(PDP), a digital micromirror device (DMD), a piezoelectric ceramic
display, or a carbon nanotube in addition to a liquid crystal
element. Note that a display device using an EL element includes an
EL display; a display device using an electron-emissive element
includes a field emission display (FED), an SED type flat panel
display (Surface-conduction Electron-emitter Display), and the
like; a display device using a liquid crystal element includes a
liquid crystal display, a transmission type liquid crystal display,
a semi-transmission type liquid crystal display, a reflection type
liquid crystal display; and a display device using electronic ink
includes electronic paper.
[0042] Note that in the invention, when it is described that an
object is formed on another object, it does not necessarily mean
that the object is in direct contact with the another object. The
case where two objects are not in direct contact with each other,
that is, the case where other object is sandwiched therebetween may
also be included. Accordingly, when it is described that a layer B
is formed on a layer A, for example, it means either the case where
the layer B is formed in direct contact with the layer A, or the
case where another layer (such as a layer C or a layer D) is formed
in direct contact with the layer A and then the layer B is formed
in direct contact with the another layer. In addition, when it is
described that an object is formed over or above another object, it
is not limited in the case where the object is in direct contact
with the another object and still another object may be sandwiched
therebetween. Accordingly, when it is described that a layer B is
formed over or above a layer A, for example, it means either the
case where the layer B is formed in direct contact with the layer
A, or the case where another layer (such as a layer C or a layer D)
is formed in direct contact with the layer A and then the layer B
is formed in direct contact with the another layer. Similarly, when
it is described that an object is formed below or under another
object, it means either the case where the objects are in direct
contact with each other or not in contact with each other.
[0043] Orientation of a liquid crystal can be controlled by
providing a cell gap adjusting film in a reflection region of a
pixel electrode, and providing a step portion thereof (a boundary
portion of the cell gap adjusting film) so as to overlap in
parallel with a slit portion at a boundary portion between a
reflection region and a transmission region. Therefore, a
semi-transmission type liquid crystal display device with high
display quality can be obtained by improving a viewing angle when
displaying an image and by suppressing deterioration of image
quality due to disorder of orientation of the liquid crystal.
BRIEF DESCRIPTION OF DRAWINGS
[0044] FIGS. 1A and 1B are diagrams showing a structure of a
display device of the invention.
[0045] FIGS. 2A to 2C are diagrams showing a structure of a display
device of the invention.
[0046] FIGS. 3A and 3B are diagrams showing a structure of a
display device of the invention.
[0047] FIGS. 4A and 4B are diagrams showing a structure of a
display device of the invention.
[0048] FIGS. 5A and 5B are diagrams showing a structure of a
display device of the invention.
[0049] FIGS. 6A and 6B are diagrams showing a structure of a
display device of the invention.
[0050] FIGS. 7A and 7B are diagrams showing a structure of a
display device of the invention.
[0051] FIGS. 8A and 8B are diagrams showing a structure of a
display device of the invention.
[0052] FIGS. 9A and 9B are diagrams showing a structure of a
display device of the invention.
[0053] FIGS. 10A and 10B are diagrams showing a structure of a
display device of the invention.
[0054] FIGS. 11A and 11B are diagrams showing a structure of a
display device of the invention.
[0055] FIGS. 12A and 12B are diagrams showing a structure of a
display device of the invention.
[0056] FIGS. 13A and 13B are diagrams showing a structure of a
display device of the invention.
[0057] FIGS. 14A and 14B are diagrams showing a structure of a
display device of the invention.
[0058] FIGS. 15A to 15D are diagrams showing a structure of a
display device of the invention.
[0059] FIGS. 16A and 16B are diagrams showing a structure of a
display device of the invention.
[0060] FIGS. 17A and 17B are diagrams showing a structure of a
display device of the invention.
[0061] FIG. 18 is a diagram showing a structure of a display device
of the invention.
[0062] FIG. 19 is a diagram showing a structure of a display device
of the invention.
[0063] FIG. 20 is a plan layout view showing a display device of
the invention.
[0064] FIG. 21 is a cross sectional view showing a display device
of the invention.
[0065] FIG. 22 is a plan layout view showing a display device of
the invention.
[0066] FIG. 23 is a cross sectional view showing a display device
of the invention.
[0067] FIG. 24 is a plan layout view showing a display device of
the invention.
[0068] FIG. 25 is a plan layout view showing a display device of
the invention.
[0069] FIG. 26 is a plan layout view showing a display device of
the invention.
[0070] FIG. 27 is a plan layout view showing a display device of
the invention.
[0071] FIG. 28 is a plan layout view showing a display device of
the invention.
[0072] FIG. 29 is a cross sectional view showing a display device
of the invention.
[0073] FIG. 30 is a cross sectional view showing a display device
of the invention.
[0074] FIG. 31 is a cross sectional view showing a display device
of the invention.
[0075] FIG. 32 is a cross sectional view showing a display device
of the invention.
[0076] FIG. 33 is a cross sectional view showing a display device
of the invention.
[0077] FIG. 34 is a cross sectional view showing a display device
of the invention.
[0078] FIG. 35 is a cross sectional view showing a display device
of the invention.
[0079] FIGS. 36A to 36C are diagrams showing a manufacturing flow
of a display device of the invention.
[0080] FIGS. 37A to 37D are diagrams showing a manufacturing flow
of a display device of the invention.
[0081] FIGS. 38A to 38C are diagrams showing a manufacturing flow
of a display device of the invention.
[0082] FIGS. 39A to 39D are diagrams showing a manufacturing flow
of a display device of the invention.
[0083] FIGS. 40A to 40D are diagrams showing a manufacturing flow
of a display device of the invention.
[0084] FIGS. 41A to 41D are diagrams showing a manufacturing flow
of a display device of the invention.
[0085] FIGS. 42A and 42B are diagrams showing a manufacturing flow
of a display device of the invention.
[0086] FIGS. 43A and 43B are cross sectional views showing a
display device of the invention.
[0087] FIG. 44 is a diagram showing an electronic apparatus to
which the invention is applied.
[0088] FIGS. 45A and 45B are diagrams showing an electronic
apparatus to which the invention is applied.
[0089] FIG. 46 is a diagram showing an electronic apparatus to
which the invention is applied.
[0090] FIG. 47 is a diagram showing an electronic apparatus to
which the invention is applied.
[0091] FIGS. 48A to 48H are diagrams showing an electronic
apparatus to which the invention is applied.
[0092] FIGS. 49A to 49F are diagrams showing a structure example of
a pixel to which the invention is applied.
DETAILED DESCRIPTION OF THE INVENTION
[0093] Although the invention will be fully described by embodiment
modes with reference to the accompanying drawings, it is to be
understood that various changes and modifications will be apparent
to those skilled in the art. Therefore, unless such changes and
modifications depart from the spirit and the scope of the
invention, they should be construed as being included therein. Note
that in a structure of the invention described below, a reference
numeral denoting the same component in a different drawing is used
commonly, and description thereof may be omitted.
Embodiment Mode 1
[0094] In this embodiment mode, description is made of a structure
of a semi-transmission type liquid crystal (which includes a
reflection region and a transmission region in one pixel, and can
be employed both as a transmission type liquid crystal and a
reflection type liquid crystal) employing a vertically aligned
liquid crystal, which has different cell gaps (a distance between
two electrodes arranged to face each other through a liquid
crystal) of a liquid crystal in the transmission region and the
reflection region, so that a display can be performed normally. A
light entering a liquid crystal is passed through the liquid
crystal twice in the reflection region, and a light is passed
through the liquid crystal once in the transmission region.
Therefore, it is required to perform a similar display in the case
of performing a display as the transmission type liquid crystal and
in the case of performing a display as the reflection type liquid
crystal, and a cell gap in the reflection region is made nearly
half of a cell gap in the transmission region so that distances
where the light is passed through the liquid crystal are almost the
same. As a method for reducing the cell gap in the reflection
region, a film is provided as a spacer in the reflection region.
Hereinafter, this film is also referred to as a cell gap adjusting
film or a film for adjusting a cell gap.
[0095] Note that the cell gap in the transmission region
corresponds to a distance between a transparent electrode and an
electrode on an opposite side across the liquid crystal, while the
cell gap in the reflection region corresponds to a distance between
an electrode (there are the case of the transparent electrode and
the case of an reflection electrode) over the cell gap adjusting
film and an electrode of an opposite side across the liquid
crystal. In the case where an electrode is uneven, the distance is
calculated using an average of a high part and a low part
thereof.
[0096] In the case of the vertically aligned liquid crystal, liquid
crystal molecules stand perpendicularly to a substrate when a
voltage is not applied to the liquid crystal, and the liquid
crystal molecules are inclined in a parallel direction when a
voltage is applied to the liquid crystal. At that time, the way an
electric field is applied and a pretilt angle of the liquid crystal
molecules are required to be controlled in order to control a
direction that the liquid crystal is inclined.
[0097] As a method for controlling a direction that the liquid
crystal is inclined when a voltage is applied, a gap like a slit is
made at an electrode, so that an electric field is supplied in a
slightly-curved direction with respect to an up-and-down direction
(the same direction as the liquid crystal vertically aligned, and a
vertical direction to the substrate and the electrode). For
example, in the case where one electrode for applying an electric
field to the liquid crystal is provided over a whole region, the
electric field is applied in an up-and-down direction appropriately
because the electric field is equally applied. However, when an
electrode is provided with a gap like a slit and a space, the
electric field curves slightly. The liquid crystal molecules are
controlled in accordance with an electric field and incline in a
parallel direction in accordance with a direction of the electric
field. Accordingly, distortion of the electric field is used for
controlling a direction that the vertically aligned liquid crystal
molecules are inclined when a voltage is applied. Therefore, it can
be prevented from a defective display due to an orientation defect
caused by the inclination of the liquid crystal molecules in
various directions.
[0098] As another method for controlling a direction that the
liquid crystal molecules are inclined, a projection (a protruding
portion) is provided over an electrode portion. The pretilt angle
of the liquid crystal molecules changes along with a projection
when provided. Accordingly, the liquid crystal molecules incline
slightly even in condition that the electric field is not supplied
to the liquid crystal; therefore, the direction that the liquid
crystal molecules are inclined can be controlled in accordance with
a slightly-inclined direction when a voltage is supplied.
[0099] Meanwhile, a cell gap adjusting film is provided in the
reflection region in order that the transmission region and the
reflection region have different cell gaps of the liquid crystal.
The cell gap adjusting film is thick, therefore influencing a
direction that the vertically aligned liquid crystal molecules are
inclined. Therefore, it is required to avoid disordering
orientation of the liquid crystal molecules and causing a
disclination in a boundary portion between the transmission region
and the reflection region (or a step portion formed by the cell gap
adjusting film).
[0100] FIGS. 1A and 1B show a relation between a reflection
electrode 101, a transparent electrode 102, and a slit 105 (a gap,
a space, or the like) of an electrode, and a cell gap adjusting
film 103. FIG. 1A is a top plan layout view. FIG. 1B is a cross
sectional view taken a line A1-A1' in FIG. 1A. As shown in FIG. 1A,
in the case where the reflection electrode 101, the transparent
electrode 102, the slit 105 (the gap, the space, or the like) of
the electrode are provided, the reflection electrode 101 and the
transparent electrode 102 are arranged approximately in parallel.
Therefore, the slit 105 (the gap, the space, or the like) of the
electrode, which is formed by the reflection electrode 101 and the
transparent electrode 102, is also arranged approximately in
parallel. The cell gap adjusting film 103 (a boundary portion or a
step portion thereof) is provided to be arranged approximately in
parallel therewith. The boundary portion (or the step portion) of
the cell gap adjusting film 103 is provided between the reflection
electrode 101 and the transparent electrode 102. As shown in FIG.
1B, the cell gap adjusting film 103 is formed over a lower layer
104, the reflection electrode 101 is formed over the cell gap
adjusting film 103, and the transparent electrode 102 is formed
over the lower layer 104.
[0101] As shown in FIG. 1B, liquid crystal molecules 106 are
oriented by providing the slit 105 (the gap, the space, or the
like) of the electrode and a protrusion of the cell gap adjusting
film 103. A direction of inclination of the liquid crystal
molecules 106 in the case where only the slit 105 (the gap, the
space, or the like) of the electrode is provided and a direction of
inclination thereof in the case where only the cell gap adjusting
film 103 is provided are almost the same. The direction of
inclination of the liquid crystal molecules 106 by providing the
slit 105 is almost the same as the direction of inclination of the
liquid crystal molecules 106 by providing the cell gap adjusting
film 103, therefore not disturbing each other. The liquid crystal
is oriented appropriately, and disorder of orientation thereof
hardly happens.
[0102] As shown in FIG. 1A, a direction of the liquid crystal is
arranged in one direction by arranging the slit 105 (the gap, the
space, or the like) of the electrode and the boundary portion (or
the step portion) of the cell gap adjusting film 103 in parallel;
therefore, orientation of the liquid crystal molecules 106 is
hardly disordered.
[0103] In the case where the liquid crystal molecules are inclined
and in a radial pattern from one point as a flower blooms, a region
in which most of the liquid crystal molecules inclined to various
directions is made at a boundary with another adjacent region;
therefore, disorder of orientation of the liquid crystal molecules
may occur. In addition, in the case where the cell gap adjusting
film is provided, orientation of the liquid crystal is affected, so
that disorder thereof may be worse. However, in the invention, the
liquid crystal is aligned in a region extended in parallel, so that
a region in which liquid crystal molecules inclined to various
directions gather is hardly made, and disorder of orientation of
the liquid crystal molecules hardly occurs.
[0104] Note that the lower layer 104 may have various structures. A
transistor, an interlayer film, glass, and the like may be
provided. A color filter, a black matrix, and the like may be
provided. In addition, the lower layer 104 is not required to be
even. Further, a transistor may be provided over an opposite
substrate but not over the lower layer 104 with the liquid crystal
sandwiched between the opposite substrate and the lower layer
104.
[0105] The slit 105 (the gap, the space, or the like) of the
electrode, the reflection electrode 101, the transparent electrode
102, and the boundary portion (or the step portion) of the cell gap
adjusting film 103 is not required to be perfectly parallel as a
part thereof or as a whole. A space, a distance and a position
thereof may be changed to some extent depending on a place if an
operation is not affected.
[0106] In the case where the slit 105 (the gap, the space, or the
like) of the electrode, the reflection electrode 101, the
transparent electrode 102, and the boundary portion (or the step
portion) of the cell gap adjusting film 103 are provided in
parallel, a length of a part in parallel therewith is not limited
as long as it is longer than at least a width of the slit 105 (the
gap, the space, or the like) of the electrode. Note that it is
preferably provided as long as possible in a pixel pitch.
[0107] The reflection electrode 101 is acceptable as long as it
reflects light. Therefore, the transparent electrode may be
provided above or below the reflection electrode. That is, a
stacked structure can be used for an electrode. A stacked structure
can be used for a part of the reflection electrode 101 or as a
whole.
[0108] The reflection electrode 101 and the transparent electrode
102 are electrically connected and operated as one electrode for
the liquid crystal; therefore, the reflection electrode 101 and the
transparent electrode 102 are required to be electrically
connected. Accordingly, when the reflection electrode 101 is
provided only over the cell gap adjusting film 103 or when the
transparent electrode 102 is not provided over the cell gap
adjusting film 103, the reflection electrode 101 and the
transparent electrode 102 cannot be electrically connected. Thus,
as shown in FIGS. 2A to 2C, the reflection electrode 101 may be
extended below the cell gap adjusting film 103 or the transparent
electrode 102 may be extended above the cell gap adjusting film 103
in order that the reflection electrode 101 and the transparent
electrode 102 are electrically connected. FIG. 2A is a top plan
layout view. FIG. 2B is a cross sectional view taken a line A1-A1'
in FIG. 2A. FIG. 2C is a cross sectional view taken a line A2-A2'
in FIG. 2A. As shown in FIG. 2C, an electrode 201 is either the
reflection electrode 101 or the transparent electrode 102, and
becomes either a transmission electrode or a reflection electrode
from a certain region. Therefore, the number of layers may be
increased in the middle of a region.
[0109] That is, the transparent electrode 102 may be in contact
with a part of the reflection electrode 101 or a whole.
[0110] Note that in one pixel, it is not preferable that the
reflection electrode 101 and the transparent electrode 102 are in a
floating state although an electric field is desired to be applied
to the liquid crystal. Therefore, as shown in FIGS. 2A and 2C, at
least a part of the reflection electrode and at least a part of the
transparent electrode may be electrically connected. As shown in
FIGS. 2B, 1A and 1B, the reflection electrode 101 and the
transparent electrode 102 may be provided separately, and a slit (a
gap, a space, or the like of electrodes) may be provided
therebetween.
[0111] Next, the description is made of a distance between the
reflection electrode 101 and the transparent electrode 102, and the
boundary portion of the cell gap adjusting film 103. The liquid
crystal molecules 106 is controlled by using the transparent
electrode 102 of a transmission region. As a method for controlling
a direction that the liquid crystal molecules are inclined, both
the slit 105 (the gap, the space, or the like) of the electrode and
the cell gap adjusting film 103 are used. As shown in FIGS. 3A and
3B, a distance d2 between the boundary portion of the cell gap
adjusting film 103 and the transparent electrode 102 may be
short.
[0112] On the other hand, liquid crystal molecules 306 are
controlled by using the reflection electrode 101. As a method for
controlling a direction that the liquid crystal molecules 306 are
inclined, only the slit 105 (the gap, the space, or the like) of
the electrode is used. Therefore, a distance d1 between the
boundary portion of the cell gap adjusting film 103 and the
reflection electrode 101 is required to be large. In the case where
the distance d1 is small, the liquid crystal molecules may be
inclined to an undesirable direction since the liquid crystal
molecules 306 are not fully controlled by the reflection electrode
101. In view of the above, the distance d1 between the boundary
portion of the cell gap adjusting film 103 and the reflection
electrode 101 is preferably larger than the distance d2 between the
boundary portion of the cell gap adjusting film 103 and the
transparent electrode 102.
[0113] In addition, as a relation to a thickness d3 of the cell gap
adjusting film, the thickness d3 of the cell gap adjusting film is
preferably smaller than the distance d1 between the boundary
portion of the cell gap adjusting film 103 and the reflection
electrode 101. By making the distance d1 between the boundary
portion of the cell gap adjusting film 103 and the reflection
electrode 101 larger than the thickness d3 of the cell gap
adjusting film, an upper surface of the cell gap adjusting film 103
is made to be even, and the liquid crystal molecules 306 can be
fully controlled.
[0114] The liquid crystal molecules 106 are controlled by using the
transparent electrode 102 of the transmission region. As a method
for controlling a direction that the liquid crystal molecules 106
are inclined, both the slit 105 (the gap, the space, or the like)
of the electrode and the call gap adjusting film 103 are used.
Therefore, the distance d2 between the boundary portion of the cell
gap adjusting film 103 and the transparent electrode 102 may be
small, or the distance d2 may be zero. In addition, instead of
providing the boundary portion of the cell gap adjusting film 103
between the reflection electrode 101 and the transparent electrode
102, the transparent electrode 102 may be provided between the
reflection electrode 101 and the boundary portion of the cell gap
adjusting film 103 as shown in FIGS. 4A and 4B. Since both the slit
105 (the gap, the space, or the like) of the electrode and the cell
gap adjusting film 103 are used as a method for controlling the
direction that the liquid crystal molecules 106 are inclined, the
liquid crystal molecules 106 are oriented appropriately without any
problems even in the case where the transparent electrode 102 is
provided between the reflection electrode 101 and the boundary
portion of the cell gap adjusting film 103 as shown in FIGS. 4A and
4B.
[0115] Although FIGS. 4A and 4B are diagrams showing the
transparent electrode 102 formed over the cell gap adjusting film
103, a structure is not limited to this. The transparent electrode
102 may be provided below the cell gap adjusting film 103 as shown
in FIGS. 5A and 5B. Note that FIGS. 4A and 5A are top plan layout
views. FIGS. 4B and 5B are cross sectional views taken a line
A1-A1' in FIGS. 4A and 5A, respectively.
[0116] A distance d2' between the boundary portion of the cell gap
adjusting film 103 and the transparent electrode 102 is preferably
smaller than the thickness d3 of the cell gap adjusting film. That
is because d2' is included in the reflection region completely when
d2' is larger than d3.
[0117] The cell gap adjusting film is preferably formed of a
material containing an organic material because of need for a
certain thickness. The material containing an organic material
preferably includes acrylic, polyimide, or polycarbonate, for
example. A thickness of the cell gap adjusting film is preferably
approximately half the cell gap of the liquid crystal because a
distance where light is passed through the liquid crystal portion
is preferably the same in the reflection region and the
transmission region. Note that it is not required to be the
complete half thereof since light often enters obliquely. It is
preferably about half the cell gap of the liquid crystal within a
range of approximately .+-.10%. Since the cell gap of the liquid
crystal is 3 to 6 .mu.m, the thickness d3 of the cell gap adjusting
film is preferably 1.1 to 3.3 .mu.m. However, the thickness of the
cell gap adjusting film is not limited to this, and the cell gap
adjusting film may have a thickness which can provide a similar
effect.
[0118] The transparent electrode 102 is preferably formed of a
conductive material with high transmissivity because it is required
to transmit light. Indium oxide-tin oxide (ITO, Indium Tin Oxide),
indium oxide-zinc oxide (IZO), or polysilicon is preferably used,
for example. The reflection electrode 101 is preferably formed of a
conductive material with high reflectivity because it is required
to reflect light. Al, Ti, or Mo is preferably used, for example.
The distance d2 between the boundary portion of the cell gap
adjusting film 103 and the transparent electrode 102 is preferably
0 to 1.1 .mu.m. The distance d2' between the boundary portion of
the cell gap adjusting film 103 and the transparent electrode 102
is preferably 0 to 1.1 .mu.m. The distance d1 between the boundary
portion of the cell gap adjusting film 103 and the reflection
electrode 101 is preferably 1.1 to 6 .mu.m since most of the
reflection electrode 101 is preferably formed over the cell gap
adjusting film 103. However, it is not limited to this.
Embodiment Mode 2
[0119] This embodiment mode describes an example other than the
case where the reflection electrode 101 is formed over the cell gap
adjusting film 103 described in Embodiment mode 1.
[0120] FIG. 6A is a top plan layout view. FIG. 6B is a cross
sectional view of FIG. 6A. As shown in FIG. 6A, in the case where a
reflection electrode 601, a transparent electrode 602, a
transparent electrode 102, a slit 605 (a gap, a space, or the like)
of an electrode are provided, the reflection electrode 601, the
transparent electrode 602 and the transparent electrode 102 are
arranged approximately in parallel, and the slit 605 (the gap, the
space, or the like) of the electrode is also arranged in parallel.
A cell gap adjusting film (a boundary portion thereof) 103 is
arranged approximately in parallel therewith. The boundary portion
of the cell gap adjusting film 103 is provided between the
reflection electrode 601 and the transparent electrode 102. As
shown in FIG. 6B, the reflection electrode 601 is formed over a
lower layer 104, over which the cell gap adjusting film 103 is
formed. The transparent electrode 602 is formed over the lower
layer 104.
[0121] Light is reflected by the reflection electrode 601 in a
reflection region, therefore light passes through the cell gap
adjusting film 103. However, in view of a refractive index, a
polarization state of light is not changed because the cell gap
adjusting film 103 is made of an isotropic material. Therefore,
light is hardly affected even when passing through the cell gap
adjusting film 103. A liquid crystal is controlled by using the
transparent electrode 602 over the cell gap adjusting film 103.
[0122] The transparent electrode 602 and the transparent electrode
102 are preferably electrically connected so as to function as one
pixel electrode and to supply an electric field to the liquid
crystal. On the other hand, the reflection electrode 601 is not
required to be electrically connected to the transparent electrode
602 and the transparent electrode 102 because it is provided for
reflecting light. However, in the case where the reflection
electrode 601 is used as an electrode for a storage capacitor, the
reflection electrode 601 may be electrically connected to the
transparent electrode 602 and the transparent electrode 102.
[0123] A distance d1' between the boundary portion of the cell gap
adjusting film 103 and the transparent electrode 602 is preferably
approximately the same as a distance d1 between the boundary
portion of the cell gap adjusting film 103 and the reflection
electrode 601. Note that it is preferable that the reflection
electrode 601 is larger than the transparent electrode 602 which
controls liquid crystal molecules because it can reflect more
light. The distance d1' between the boundary portion of the cell
gap adjusting film 103 and the transparent electrode 602 is
preferably larger than the distance d1 between the boundary portion
of the cell gap adjusting film 103 and the reflection electrode
601. The distance d1' between the boundary portion of the cell gap
adjusting film 103 and the transparent electrode 602 is preferably
1.1 to 7 .mu.m. However, it is not limited to this.
[0124] Note that the reflection electrode 601 is not required to be
provided over the lower layer 104. The reflection electrode 601 in
the reflection region is provided only for reflecting light;
therefore, it may be provided in or below the lower layer 104.
[0125] In addition, a plurality of the reflection electrodes 601
may be provided. For example, a part of the reflection electrodes
601 may be provided over the lower layer 104, and another part of
the reflection electrodes 601 may be provided in the lower layer
104.
[0126] The reflection electrode may be used also as an electrode
which is used for another purpose. For example, the reflection
electrode may be used also as an electrode for forming a storage
capacitor.
[0127] Note that description in this embodiment mode is the
description in Embodiment Mode 1 a part of which is changed.
Therefore, the description in Embodiment Mode 1 can be applied to
the description in this embodiment mode.
Embodiment Mode 3
[0128] Although description is made of the case where the
reflection electrode is even in Embodiment Modes 1 and 2, it is not
limited to this. When the reflection electrode is uneven, light is
diffused; therefore, a whole luminance is averaged and a clear
image can be obtained in the case of performing a display of
reflecting mode.
[0129] FIGS. 7A and 7B show an example of the case where the
reflection electrode has an uneven portion. An upper surface of a
cell gap adjusting film 703 has an uneven portion. As a result, a
reflection electrode 701 which is formed over the cell gap
adjusting film 703 has an uneven portion. Note that it is not
preferable that the uneven portion be too large because a large
uneven portion affects a direction that the liquid crystal is
inclined. Therefore, a thickness d4 of a projecting portion of the
cell gap adjusting film 703 is preferably smaller than the
thickness d3 of the cell gap adjusting film 703. For example, the
thickness d4 of the projecting portion of the cell gap adjusting
film 703 is preferably 0.5 .mu.m or less. However, it is not
limited to this.
[0130] In addition, the projecting portion of the cell gap
adjusting film 703 is preferably arranged approximately in parallel
with the slit 105 (the gap, the space, or the like) of the
electrode, the transparent electrode 102, and the reflection
electrode 701 as shown in FIG. 7A. By being arranged approximately
in parallel, disorder of orientation of the liquid crystal can be
reduced, and light can be diffused.
[0131] Note that in the case where the thickness d4 of the
projecting portion of the cell gap adjusting film 703 is small, the
projecting portion of the cell gap adjusting film 703 may be
arranged in random as shown in FIG. 8A. FIG. 8B is a cross
sectional view taken a line A1-A1' in FIG. 8A.
[0132] The cell gap adjusting film 703 may have a stacked-layer
structure. For example, the cell gap adjusting film 703 is formed
by forming a flat portion, and an uneven portion over the flat
portion.
[0133] Unevenness may be formed by forming an object over the cell
gap adjusting film 703, and forming the reflection electrode 701
thereover. The object is not the cell gap adjusting film 703. For
example, an uneven portion may be formed by forming the transparent
electrode in accordance with unevenness, and forming the reflection
electrode 701 thereover.
[0134] As shown in FIGS. 6A and 6B, in the case where the
reflection electrode is formed below the cell gap adjusting film,
light can be diffused by making a surface of the reflection
electrode uneven. This case is shown in FIGS. 9A and 9B. A lower
layer 904 is provided with an uneven portion, over which a
reflection electrode 901 is formed, over which a cell gap adjusting
film 903 is formed. The transparent electrode 602 is formed over
the cell gap adjusting film 903. The transparent electrode 602 is
flat, so that orientation of the liquid crystal thereover is not
disturbed. By using this structure, light can be diffused without
disturbing orientation of the liquid crystal molecules.
[0135] For example, a thickness d5 of a projecting portion of the
lower layer 904 is preferably 1.0 .mu.m or less. Therefore, light
can be sufficiently diffused. However, it is not limited to
this.
[0136] In FIG. 9A, although a projecting portion of the lower layer
904 is arranged approximately in parallel with the slit 605 (the
gap, the space, or the like) of the electrode, the transparent
electrode 102, the reflection electrode 901, and the transparent
electrode 602, it is not limited to this. The projecting portion of
the reflection electrode 901 may be arranged in random as shown in
FIG. 10A. It is preferable to be arranged in random because a
profound effect on light diffusion can be obtained. Note that FIGS.
9B and 10B are cross sectional views taken a line A3-A3' in FIGS.
9A and 10B, respectively.
[0137] In the case where the lower layer 904 is provided with the
uneven portion as in FIGS. 9A, 9B, 10A, and 10B, the projecting
portion may be formed of a material containing an organic material.
The material containing an organic material preferably includes
acrylic, polyimide, or polycarbonate, for example. Alternatively, a
wire, an electrode, or the like may be formed in accordance with
the uneven portion, over which an interlayer film may be formed by
using a film with poor planarity. For example, a film containing
silicon oxide or silicon nitride is provided over a wire or an
electrode, thereby the uneven portion of the lower layer 904 may be
formed.
[0138] Note that description in this embodiment mode is the
description in Embodiment Modes 1 and 2 a part of which are changed
or improved. Therefore, the description in Embodiment Modes 1 and 2
can be applied to the description in this embodiment mode.
Embodiment Mode 4
[0139] The boundary portion between the reflection region and the
transmission region is described in the aforementioned embodiment
modes. In this embodiment mode, each of the reflection region and
the transmission region and the like are also described.
[0140] FIG. 11A is a top plan layout view. FIG. 11B is a cross
sectional view taken along lines A4-A4' and A5-A5' in FIG. 11A. As
shown in FIGS. 11A and 11B, a slit (a gap, a space, or the like) of
an electrode is formed in the reflection region and the
transmission region. When a slit 1105a (a gap, a space, or the
like) of an electrode in the reflection region is compared with a
slit 1105b (a gap, a space, or the like) of an electrode in the
transmission region, a width d6 of the slit 1105a (the gap, the
space, or the like) of the electrode in the reflection region is
preferably larger than a width d7 of the slit 1105b (the gap, the
space, or the like) of the electrode in the transmission region. As
shown in FIG. 11B, liquid crystal molecules 1106a and 1106b are
controlled by using the slit 1105a (the gap, the space, or the
like) of the electrode in the reflection region, while liquid
crystal molecules 1106c and 1106d are controlled by using the slit
1105b (the gap, the space, or the like) of the electrode in the
transmission region. In this case, in the reflection region, a cell
gap of the liquid crystal is smaller than that in the transmission
region because of having the cell gap adjusting film 103;
therefore, distortion of the electric field is not enough unless
the slit 1105a (the gap, the space, or the like) of the electrode
is made to be large. In addition, an electrode on an opposite side
across the liquid crystal molecules is provided with an orientation
film, thereby orientation of the liquid crystal molecules is
controlled. When the cell gap of the liquid crystal is small, it
becomes difficult to move the liquid crystal molecules by supplying
the electric field because an effect of the orientation film of an
electrode of an opposite side is large. For the aforementioned
reasons, the width d6 of the slit 1105a (the gap, the space, or the
like) of the electrode in the reflection region is preferably
larger than the width d7 of the slit 1105b (the gap, the space, or
the like) of the electrode in the transmission region.
[0141] As shown in FIGS. 12A and 12B, when a width d8 of a slit
1205a (a gap, a space, or the like) of an electrode in the boundary
portion between the reflection region and the transmission region
is compared with the width d7 of the slit 1105b (the gap, the
space, or the like) of the electrode in the transmission region,
the width d8 is preferably larger than the width d7. This is
because the width d8 includes a function of controlling the liquid
crystal in the reflection region. The width d8 is required to be
large in order to control the liquid crystal sufficiently. Note
that FIG. 12A is a top plan layout view. FIG. 12B is a cross
sectional view taken a line A6-A6' in FIG. 12A.
[0142] As shown in FIGS. 13A and 13B, when the width d8 of the slit
1205a (the gap, the space, or the like) of the electrode in the
boundary portion between the reflection region and the transmission
region is compared with the width d6 of the slit 1105a (the gap,
the space, or the like) of the electrode in the transmission
region, the width d8 is preferably almost equal to the width d6.
This is because both of the widths include control of the liquid
crystal in the reflection region. Note that FIG. 13A is a top plan
layout view. FIG. 13B is a cross sectional view taken a line A7-A7'
in FIG. 13A.
[0143] For example, the width d8 of the slit 1205a (the gap, the
space, or the like) of the electrode in the boundary portion
between the reflection region and the transmission region is
preferably 1.1 to 10.0 .mu.m. The width d6 of the slit 1105a (the
gap, the space, or the like) of the electrode in the reflection
region is preferably 1.1 to 10.0 .mu.m. The width d7 of the slit
1105b (the gap, the space, or the like) of the electrode in the
transmission region is preferably 1.0 to 9.0 .mu.m. However, they
are not limited to these.
[0144] Note that description in this embodiment mode is the
description in Embodiment Modes 1 to 3 a part of which are changed,
improved or detailed. Therefore, the description in Embodiment
Modes 1 to 3 can be applied to the description in this embodiment
mode.
Embodiment Mode 5
[0145] The liquid crystal molecules 106 described in FIGS. 1A and
1B are inclined in one direction. However, in the case where the
liquid crystal molecules in one pixel are inclined only in one
direction, a viewing angle is narrow. That is, the way the liquid
crystal looks is changed when seen from a certain direction because
the direction that the liquid crystal molecules are inclined looks
different depending on a viewpoint.
[0146] The liquid crystal molecules are not preferably inclined in
only one direction, but they are preferably inclined in various
directions. That is, it is preferable to employ a multi-domain
structure and have a plurality of regions so as to provide a
plurality of directions that the liquid crystal molecules are
inclined. For example, in the case where the liquid crystal is
inclined in a certain direction, a region where the liquid crystal
is inclined in an opposite direction is preferably formed.
[0147] A projection (a protruding portion) or a slit (a gap, a
space, or the like) can be provided on an electrode portion so that
the liquid crystal is inclined in the opposite direction.
[0148] FIGS. 14A and 14B are configuration diagrams in the case
where the liquid crystal is inclined in right side and in the case
where the liquid crystal is inclined in left side in portions
adjacent to the cell gap adjusting film 103. Note that FIG. 14A is
a top plan layout view. FIG. 14B is a cross sectional view taken a
line A8-A8' in FIG. 14A. By providing slits 1405a and 1405b (a gap,
a space, or the like) of an electrode in parallel on both sides of
the reflection electrode 101, each liquid crystal molecules are
inclined in opposite directions each other like the liquid crystal
molecules 1406a and 1406b. Consequently, the ways the liquid
crystal molecules look can be averaged; therefore, a viewing angle
can be increased.
[0149] Note that in FIGS. 14A and 14B, although a plane on which
the liquid crystal is inclined is on the same plane as A8-A8', it
is not limited to this. As shown in FIGS. 15A, 15B, 15C and 15D, a
cross section A9-A9' and a cross section A10-A10' may be arranged
perpendicular to each other, which can increase a viewing angle.
Note that FIGS. 15A and 15B are top plan layout views. FIG. 15C is
a cross sectional view taken a line A9-A9' in FIG. 15A. FIG. 15D is
a cross sectional view taken a line A10-A10' in FIG. 15C.
[0150] In addition, FIGS. 15A, 15B, 15C and 15D and FIGS. 14A and
14B may be combined. That is, the liquid crystal molecules may be
set to move on different planes like the cross section A9-A9' and
the cross section A10-A10', and the liquid crystal molecules on the
same plane may be set to be inclined in various directions like a
cross section A8-A8'.
[0151] In the case where the liquid crystal molecules are inclined
and in a radial pattern from one point as a flower blooms, a region
in which most of the liquid crystal molecules inclined to various
directions is made at a boundary with another adjacent region;
therefore, disorder of orientation of the liquid crystal molecules
may occur. However, in the invention, the liquid crystal is aligned
in a region extended in parallel; therefore, disorder of
orientation of the liquid crystal molecules hardly occurs.
[0152] Note that description in this embodiment mode is the
description in Embodiment Modes 1 to 4 a part of which are changed,
improved or detailed. Therefore, the description in Embodiment
Modes 1 to 4 can be applied to the description in this embodiment
mode.
Embodiment Mode 6
[0153] An electrode on one side is described in the aforementioned
embodiment modes. Actually, an electrode and a substrate are
provided on an opposite side, across the liquid crystal. A
projection on an electrode portion, a slit (a gap, a space, or the
like) of an electrode, and the like are required to be provided on
this opposite substrate in order that the liquid crystal molecules
are easily inclined.
[0154] FIGS. 16A and 16B show an example in which a slit 1605 (a
gap, a space, or the like) of an electrode is provided over an
opposite substrate 1604. FIG. 16A is a top plan layout view. FIG.
16B is a cross sectional view taken a line A11-A11' in FIG. 16A. As
shown in FIG. 16B, transparent electrodes 1601 and 1602 and the
like are provided over the opposite substrate 1604, which is not
required to reflect light. The slit 1605 (the gap, the space, or
the like) of the electrode on the opposite substrate 1604 is
preferably arranged approximately in the middle of the reflection
electrode 101 and the transparent electrodes. Therefore, liquid
crystal molecules 1606 which are inclined in each direction are
arranged evenly.
[0155] In addition, as shown in FIG. 16A that is a plan view, the
slit 1605 (the gap, the space, or the like) of the electrode on the
opposite substrate 1604 and the transparent electrodes 1601 and
1602 on the opposite substrate are arranged approximately in
parallel with the slit 105 (the gap, the space, or the like) of the
electrode, the transparent electrode 102, and the reflection
electrode 101. Therefore, disorder of orientation of the liquid
crystal can be reduced because the direction that the liquid
crystal is inclined can be controlled appropriately by both
substrates between which the liquid crystal is sandwiched.
[0156] Next, FIGS. 17A and 17B show the case where a projection
1705 is provided on the opposite substrate 1604. FIG. 17A is a top
plan layout view. FIG. 17B is a cross sectional view taken a line
A11-A11' in FIG. 17A. As shown in FIG. 17B that is a cross
sectional view, a transparent electrode 1701 is provided to cover
the projection 1705. However, it is not limited to this. The
transparent electrode may be provided between the projection 1705
and the opposite substrate 1604. An orientation film is provided at
a portion in contact with the liquid crystal molecules. Therefore,
in the case of FIG. 17B, the orientation film is provided to cover
the transparent electrode 1701. The projection 1705 on the opposite
substrate 1604 is preferably arranged approximately in the middle
of the reflection electrode 101 and the transparent electrodes.
Therefore, liquid crystal molecules 1706 which are inclined in each
direction are arranged evenly.
[0157] In addition, as shown in FIG. 17A that is a plan view, the
projection 1705 over the opposite substrate 1604 is arranged
approximately in parallel with the slit 105 (the gap, the space, or
the like) of the electrode, the transparent electrode 102, and the
reflection electrode 101. Therefore, disorder of orientation of the
liquid crystal can be reduced because the direction that the liquid
crystal is inclined can be controlled appropriately by both
substrates between which the liquid crystal is sandwiched.
[0158] Next, description is made of a width of the slit (the gap,
the space, or the like) of the electrode with reference to a cross
sectional view shown in FIG. 18. In FIG. 18, when a width d10 of a
slit 1805b (a gap, a space, or the like) of the transparent
electrode on the opposite substrate 1604 in the reflection region
is compared with a width d9 of a slit 1805a (a gap, a space, or the
like) of the transparent electrode on the opposite substrate 1604
in the transmission region, the width d9 is preferably smaller than
the width d10. The relation between the width d9 and the width d10
is similar to the relation between the width d6 of the slit 1105a
(the gap, the space, or the like) of the electrode in the
reflection region and the width d7 of the slit 1105b (the gap, the
space, or the like) of the electrode in the transmission
region.
[0159] A cell gap of the liquid crystal in the reflection region is
smaller than that in the transmission region because of having the
cell gap adjusting film 103; therefore, distortion of the electric
field is not enough unless the slit 1805b (the gap, the space, or
the like) of the electrode is made to be large. Consequently, the
width d10 of the slit 1805b (the gap, the space, or the like) of
the electrode in the reflection region is preferably larger than
the width d9 of the slit 1805a (the gap, the space, or the like) of
the electrode in the transmission region.
[0160] In addition, the width d6 of the slit 1105a (the gap, the
space, or the like) of the electrode in the reflection region shown
in FIGS. 13A and 13B is preferably approximately equal to the width
d10 of the slit 1805b (the gap, the space, or the like) of the
electrode on the opposite substrate 1604 in the reflection region
shown in FIG. 18. This is because if the width d6 and the width d10
are the same, a symmetry property is improved and the liquid
crystal is arranged evenly; therefore, an orientation defect of the
liquid crystal can be reduced.
[0161] Similarly, the width d7 of the slit 1205b (the gap, the
space, or the like) of the electrode in the transmission region
shown in FIGS. 12A and 12B is preferably approximately equal to the
width d9 of the slit 1805a (the gap, the space, or the like) of the
electrode in the transmission region shown in FIG. 18. This is
because if the width d6 and the width d9 are the same, a symmetry
property is improved and the liquid crystal is arranged evenly;
therefore, an orientation defect of the liquid crystal can be
reduced.
[0162] Next, description is made of a width of a projection of an
electrode portion with reference to a cross sectional view shown in
FIG. 19. In FIG. 19, when a width d12 of a projection 1905b on the
opposite substrate 1604 in the reflection region is compared with a
width d11 of a projection 1905a on the opposite substrate 1604 in
the transmission region, the width d11 is preferably smaller than
the width d12. The relation between the width d11 and the width d12
is similar to the relation between the width d6 of the slit 1105a
(the gap, the space, or the like) of the electrode in the
reflection region and the width d7 of the slit 1105b (the gap, the
space, or the like) of the electrode in the transmission
region.
[0163] A cell gap of the liquid crystal in the reflection region is
smaller than that in the transmission region because of having the
cell gap adjusting film 103; therefore, distortion of the electric
field is not enough unless the projection 1905b is made to be
larger. Consequently, the width d12 of the projection 1905b in the
reflection region is preferably larger than the width d11 of the
projection 1905a in the transmission region.
[0164] In addition, the width d6 of the slit 1105a (the gap, the
space, or the like) of the electrode in the reflection region shown
in FIGS. 13A and 13B is preferably approximately the same as the
width d12 of the projection 1905b on the opposite substrate 1604 in
the reflection region. This is because if the width d6 and the
width d12 are the same, a symmetry property is improved and the
liquid crystal is arranged evenly; therefore, an orientation defect
of the liquid crystal can be reduced.
[0165] Similarly, the width d7 of the slit 1205b (the gap, the
space, or the like) of the electrode in the reflection region shown
in FIGS. 12A and 12B is preferably approximately equal to the width
d11 of the projection 1905a on the opposite substrate 1604 in the
transmission region shown in FIG. 18. This is because if the width
d7 and the width d11 are the same, a symmetry property is improved
and the liquid crystal is arranged evenly; therefore, an
orientation defect of the liquid crystal can be reduced.
[0166] In addition, the opposite substrate 1604 may have
unevenness. Light is reflected diffusely by the unevenness;
therefore, whole luminance is averaged and a clear image can be
obtained. That is, a liquid crystal display device with certain
brightness can be obtained when seen from any direction. As a
result, light reaches a viewer of a display well, and luminance is
increased substantially.
[0167] In addition, the opposite substrate 1604 is provided with
the cell gap adjusting film. A film thickness can be adjusted
easily by providing the cell gap adjusting films on both sides
between which the liquid crystal is sandwiched in order to make a
thickness of the cell gap adjusting film thicker. Note that the
cell gap adjusting film which is provided over the opposite
substrate 1604 can have unevenness as shown in Embodiment Mode
3.
[0168] Note that description in this embodiment mode can commonly
used for the description in Embodiment Modes 1 to 5. Therefore, the
description in Embodiment Modes 1 to 5 can be combined with the
description in this embodiment mode.
Embodiment Mode 7
[0169] FIG. 20 shows a top plan layout view in the case where a
transistor and various wires are provided over the above-described
lower layer 104. Note that FIG. 20 shows the case where a bottom
gate transistor is employed as a transistor. A gate signal line
2001 and a capacitor line 2002 which are formed of the same
material in the same layer are provided in a lateral direction. A
part of the gate signal line 2001 functions as a gate electrode of
the transistor. A part of the capacitor line 2002 functions as an
electrode of a storage capacitor. A gate insulating film is formed
to cover a whole area. Note that the gate insulating film is not
shown in FIG. 20 because FIG. 20 is a plan layout view.
[0170] Silicon 2003 is formed over the gate insulating film. This
portion functions as a transistor, over which a source signal line
2004, a drain electrode 2005 and a reflection electrode 2006 which
are formed of the same material in the same layer are provided. A
storage capacitor is formed between the reflection electrode 2006
and the capacitor line 2002. Note that as an electrode of the
storage capacitor, a pixel electrode 2007 may be employed instead
of the reflection electrode 2006. An interlayer insulating film is
formed to cover a whole area over the source signal line 2004, the
drain signal line 2005 and the reflection electrode 2006. The
interlayer insulating film is not described in FIG. 20 because FIG.
20 is a top plan layout view. Contact holes 2008 and 2009 are
provided in the interlayer insulating film. A cell gap adjusting
film 2010 is formed over the interlayer insulating film in the
reflection region, over which a transparent conductive film 2011 is
formed.
[0171] In the layout view shown in FIG. 20, the cell gap adjusting
film 2010 is formed over the reflection electrode 2006; therefore,
the case of FIGS. 6A and 6B is used here. In addition, the storage
capacitor is provided in the reflection region; therefore, an area
of the transmission region can be made large.
[0172] As shown in the layout view of FIG. 20, a region where a
slit (a gap, a space, or the like) of an electrode and a boundary
of the cell gap adjusting film 2010 are provided in parallel is
formed; therefore, orientation of the liquid crystal is performed
appropriately. In addition, a region where the transparent
conductive film 2011 and the boundary of the cell gap adjusting
film 2010 are provided in parallel is formed; therefore,
orientation of the liquid crystal is performed appropriately.
[0173] The cell gap adjusting film 2010, the electrode, the slit,
and the like are provided similarly to those shown in FIGS. 14A,
14B, 15A, 15B, 15C and 15D; therefore, a viewing angle can be
increased.
[0174] FIG. 21 shows a cross sectional view taken a line B1-B1' in
FIG. 20. The storage capacitor is provided in the reflection region
as shown in FIG. 21. Two electrodes of the storage capacitor are
used also as the reflection electrode. Note that the gate
insulating film and the interlayer insulating film, which are not
shown in FIG. 20, are described as a gate insulating film 2101 and
an interlayer insulating film 2102 in FIG. 21.
[0175] Next, FIG. 22 shows a layout view in the case of a top gate
transistor. Silicon 2203 is provided, over which a gate insulating
film 2301 is formed to cover a whole area. The gate insulating film
2301 is not described in FIG. 22 because FIG. 22 is a top plan
layout view. A gate signal line 2201 and a capacitor line 2202
which are formed of the same material in the same layer are
provided in a lateral direction over the gate insulating film 2301.
A part of the gate signal line 2201 which is formed over the
silicon 2203 functions as a gate electrode of the transistor. A
part of the capacitor line 2202 functions as an electrode of the
storage capacitor. An interlayer insulating film 2302 is formed
thereover to cover a whole area. The interlayer insulating film
2302 is not described in FIG. 22 because FIG. 22 is a plan layout
view. A source signal line 2204, a drain signal line 2205 and a
reflection electrode 2206 which are formed of the same material in
the same layer are formed over the interlayer insulating film 2302.
The storage capacitor is formed between the reflection electrode
2206 and the capacitor line 2202. Note that as the electrode of the
storage capacitor, an electrode in the same layer as the silicon
2203 may be used, and the storage capacitor may be formed between
the electrode and the capacitor line 2002. An interlayer insulating
film 2303 is formed thereover to cover a whole area. The interlayer
insulating film 2303 is not described in FIG. 22 because FIG. 22 is
a top plan layout view. A cell gap adjusting film 2210 is formed
over the interlayer insulating film 2303 in the reflection region,
over which a transparent conductive film 2211 is formed.
[0176] In the layout view shown in FIG. 22, the cell gap adjusting
film 2210 is formed over the reflection electrode 2206; therefore,
the case of FIGS. 6A and 6B is used here.
[0177] In addition, the storage capacitor is provided in the
reflection region; therefore, an area of the transmission region
can be made large. As shown in this layout view, a region where a
slit (a gap, a space, or the like) of an electrode and a boundary
of the cell gap adjusting film 2210 are provided in parallel is
provided; therefore, orientation of the liquid crystal is performed
appropriately. In addition, a region where the transparent
conductive film 2211 and the boundary of the cell gap adjusting
film 2210 are provided in parallel is provided; therefore,
orientation of the liquid crystal is performed appropriately.
[0178] The cell gap adjusting film, the electrode, the slit, and
the like are provided similarly to those shown in FIGS. 14A, 14B,
15A, 15B, 15C and 15D; therefore, a viewing angle can be
increased.
[0179] FIG. 23 shows a cross sectional view taken a line B2-B2' in
FIG. 22. The storage capacitor is provided in the reflection region
as shown in FIG. 23. Two electrodes of the storage capacitor are
used also as the reflection electrode.
[0180] Note that description in this embodiment mode can commonly
used for the description in Embodiment Modes 1 to 6. Therefore, the
description in Embodiment Modes 1 to 6 can be combined with the
description in this embodiment mode.
Embodiment Mode 8
[0181] FIGS. 20 and 22 show examples of the layout views of the
transparent electrode and the reflection electrode. Next, some
examples of the electrode is described.
[0182] FIG. 24 shows an example of a layout view of an electrode.
In over an electrode 2411, slits 2405 (a gap, a space, or the like)
of an electrode are provided in two oblique directions. Reference
numerals 2403a, 2403b, and 2403c correspond to boundary portions of
the cell gap adjusting films. The cell gap adjusting film is
provided in a portion enclosed by a dotted line. A large part of
this boundary is arranged approximately in parallel with the slits
2405 (the gap, the space, or the like) of the electrode. Therefore,
an orientation defect of the liquid crystal can be reduced.
[0183] One or a plurality of the cell gap adjusting films can be
provided. That is, only the cell gap adjusting film 2403a may be
provided, or two films of the cell gap adjusting film 2403b and the
cell gap adjusting film 2403c may be provided. Alternatively, all
of the cell gap adjusting films 2403a, 2403b, and 2403c may be
provided. The cell gap adjusting film 2403a has two directions of
slits, which are an obliquely upper right direction and an
obliquely upper left direction. Therefore, a viewing angle can be
increased due to a plurality of directions that the liquid crystal
molecules are inclined. Similarly, when two films of the cell gap
adjusting film 2403b and the cell gap adjusting film 2403c are
employed, a viewing angle can be increased because of a plurality
of directions that the liquid crystal molecules are inclined.
[0184] A portion where the cell gap adjusting film exists serves as
the reflection region, and the reflection electrode is formed in
the reflection region. An electrode 2411 in the portion where the
cell gap adjusting film exists may become the reflection electrode.
Alternatively, the reflection electrode may be provided below the
cell gap adjusting film as shown in FIGS. 21 and 23. A portion
where the cell gap adjusting film does not exist becomes the
transmission region. The reflection electrode and the transparent
electrode are both in the case where they are electrically
connected as one electrode as shown in FIGS. 2A to 2C and in the
case where they are different electrodes as shown in FIGS. 6A and
6B.
[0185] Another example of the electrode is shown in FIG. 25. In an
electrode 2511, slits 2505 (a gap, a space, or the like) of an
electrode is provided in two oblique directions. A reference
numeral 2503 corresponds to the boundary portion of the cell gap
adjusting film. The cell gap adjusting film is provided in a
portion enclosed by a dotted line. A large part of this boundary is
arranged approximately in parallel with the slits 2505 (the gap,
the space, or the like) of the electrode. Therefore, an orientation
defect of the liquid crystal can be reduced.
[0186] In addition, the slits 2505 (the gap, the space, or the
like) of the electrode is long and not being cut as shown in FIG.
24. Therefore, an orientation defect of the liquid crystal can be
reduced.
[0187] Note that a portion where the cell gap adjusting film exists
serves as the reflection region, and the reflection electrode is
formed in the reflection region. The electrode 2511 in the portion
where the cell gap adjusting film exists may serve as the
reflection electrode. Alternatively, the reflection electrode may
be provided below the cell gap adjusting film as shown in FIGS. 21
and 23. A portion where the cell gap adjusting film does not exist
becomes the transmission region. The reflection electrode and the
transparent electrode are both in the case where they are
electrically connected as one electrode as shown in FIGS. 2A to 2C
and in the case where they are different electrodes as shown in
FIGS. 6A and 6B.
[0188] Another example of the electrode is shown in FIG. 26. A slit
2605 (a gap, a space, or the like) of an electrode is provided at
an electrode 2611. The slit has a shape of teeth of a comb. Cell
gap adjusting films 2603a and 2603b may be provided along an
envelope like passing a tip of the shape of teeth of a comb. Note
that the cell gap adjusting films 2603a and 2603b may be provided
along the shape of teeth of a comb. The cell gap adjusting film is
provided in a portion enclosed by a dotted line of the cell gap
adjusting films 2603a and 2603b. A large part of this boundary is
arranged approximately in parallel with the slit 2605 (the gap, the
space, or the like) of the electrode or the envelope. Therefore, an
orientation defect of the liquid crystal can be reduced.
[0189] A portion where the cell gap adjusting film exists becomes
the reflection region, and the reflection electrode is formed in
the reflection region. An electrode 2611 in the portion where the
cell gap adjusting film exists may become the reflection electrode.
Alternatively, the reflection electrode may be provided below the
cell gap adjusting film as shown in FIGS. 21 and 23. A portion
where the cell gap adjusting film does not exist becomes the
transmission region. The reflection electrode and the transparent
electrode are both in the case where they are electrically
connected as one electrode as shown in FIGS. 2A to 2C and in the
case where they are different electrodes as shown in FIGS. 6A and
6B.
[0190] Another example of the electrode is shown in FIG. 27. In an
electrode 2711, slits 2705 (a gap, a space, or the like) of an
electrode has a dogleg shape and is provided in two oblique
directions. Reference numerals 2703a and 2703b correspond to the
boundary portions of the cell gap adjusting film. The cell gap
adjusting film is provided in a portion enclosed by a dotted line.
A large part of this boundary is arranged approximately in parallel
with the slits 2705 (the gap, the space, or the like) of the
electrode. Therefore, an orientation defect of the liquid crystal
can be reduced.
[0191] One or a plurality of the cell gap adjusting films can be
provided. That is, only the cell gap adjusting film 2703a or the
cell gap adjusting film 2703b may be provided, or two films of the
cell gap adjusting film 2703a and the cell gap adjusting film 2703b
may be provided. When the cell gap adjusting film 2703a and the
cell gap adjusting film 2703b are employed, a viewing angle can be
increased because of a plurality of directions that the liquid
crystal molecules are inclined.
[0192] A portion where the cell gap adjusting film exists serves as
the reflection region, and the reflection electrode is formed in
the reflection region. The electrode 2711 in the portion where the
cell gap adjusting film exists may serve as the reflection
electrode. Alternatively, the reflection electrode may be provided
below the cell gap adjusting film as shown in FIGS. 21 and 23. A
portion where the cell gap adjusting film does not exist becomes
the transmission region. The reflection electrode and the
transparent electrode are both in the case where they are
electrically connected as one electrode as shown in FIGS. 2A to 2C
and in the case where they are different electrodes as shown in
FIGS. 6A and 6B.
[0193] Another example of the electrode is shown in FIG. 28. In an
electrode 2811, slits 2805 (a gap, a space, or the like) of an
electrode is provided in two oblique directions. The electrode 2811
is provided like a branch growing from a trunk. A reference numeral
2803 corresponds to the boundary portion of the cell gap adjusting
film. The cell gap adjusting film is provided in a portion enclosed
by a dotted line. A large part of this boundary is arranged
approximately in parallel with the electrode 2811. Therefore, an
orientation defect of the liquid crystal can be reduced.
[0194] A portion where the cell gap adjusting film exists serves as
the reflection region, and the reflection electrode is formed in
the reflection region. The electrode 2811 in the portion where the
cell gap adjusting film exists may serve as the reflection
electrode. Alternatively, the reflection electrode may be provided
below the cell gap adjusting film as shown in FIGS. 21 and 23. A
portion where the cell gap adjusting film does not exist becomes
the transmission region. The reflection electrode and the
transparent electrode are both in the case where they are
electrically connected as one electrode as shown in FIGS. 2A to 2C
and in the case where they are different electrodes as shown in
FIGS. 6A and 6B.
[0195] Note that a layout view of the electrode is not limited to
those described in this embodiment mode.
[0196] Note that description in this embodiment mode can commonly
used for the description in Embodiment Modes 1 to 7. Therefore, the
description in Embodiment Modes 1 to 7 can be combined with the
description in this embodiment mode.
Embodiment Mode 9
[0197] FIGS. 21 and 23 show cross-sectional structural views in the
case of employing the bottom gate transistor and the case of
employing the top gate transistor. In this embodiment mode, another
cross-sectional structural view is described. Note that a
cross-sectional structure is not limited to those described in this
embodiment mode.
[0198] FIG. 29 shows an example of a cross sectional view in the
case of employing the bottom gate transistor. A gate signal line
2901 and a capacitor line 2902 are formed of the same material in
the same layer. A part of the gate signal line 2901 functions as a
gate electrode of the transistor. A part of the capacitor line 2902
functions as an electrode of the storage capacitor. A gate
insulating film 2991 is formed thereover. Silicon 2903 is formed
over the gate insulating film 2991. This portion functions as the
transistor. A source signal line 2904 and a drain signal line 2905
are formed over the silicon 2903. A capacitor electrode 2906 is
formed of the same material in the same layer as the source signal
line 2904 and the drain signal line 2905. The storage capacitor is
formed between the capacitor electrode 2906 and the capacitor line
2902. An interlayer insulating film 2992 is formed over the source
signal line 2904, the drain signal line 2905, and the capacitor
electrode 2906, over which a cell gap adjusting film 2910 is
formed.
[0199] In the structure shown in FIG. 29, the cell gap adjusting
film 2910 is eliminated at least from the transmission region. The
cell gap adjusting film 2910 may be eliminated from a region other
than the reflection region. A reflection electrode 2913 is formed
over the cell gap adjusting film 2910. Note that a contact
electrode 2912 is not required to be provided. A transparent
electrode 2911 is formed over the reflection electrode 2913. By
providing the transparent electrode 2911 over the reflection
electrode 2913, the transparent electrode 2911 and the reflection
electrode 2913 are electrically connected.
[0200] As the electrode of the storage capacitor, the transparent
electrode 2911 and the reflection electrode 2913 may be employed
instead of the capacitor electrode 2906. At that time, a thick
material is preferably eliminated because an insulating film
between the electrodes is preferably as thin as possible in order
to make a capacitance value large.
[0201] In FIG. 29, although the transparent electrode 2911 is
formed over the reflection electrode 2913, it is not limited to
this. The reflection electrode 2913 may be formed over the
transmission region 2911.
[0202] Although the interlayer insulating film 2992 is formed over
the source signal line 2904, the drain signal line 2905, and the
capacitor electrode 2906, it is not limited to this. If
circumstances require, the interlayer insulating film 2992 is
provided.
[0203] Note that in FIG. 29, although the reflection electrode 2913
is provided, it is not limited to this. The reflection electrode
may be formed by sharing the drain electrode 2905, an electrode or
a wire in the same layer thereof, the capacitor line 2902, or an
electrode or a wire in the same layer thereof, or by forming a new
electrode.
[0204] Next, in the case where the reflection electrode with
unevenness is formed below the cell gap adjusting film as shown in
FIGS. 9A and 9B, FIG. 30 shows an example of a cross sectional view
in the case of employing the bottom gate transistor A gate signal
line 3001 and a capacitor line 3002 are formed of the same material
in the same layer. A part of the gate signal line 3001 functions as
a gate electrode of the transistor. A part of the capacitor line
3002 functions as an electrode of the storage capacitor. A gate
insulating film 3091 is formed thereover. Silicon 3003 is formed
over the gate insulating film 3091. This portion functions as the
transistor. A source signal line 3004 and a drain signal line 3005
are formed over the silicon 3003. A capacitor electrode 3006 is
formed of the same material in the same layer as the source signal
line 3004 and the drain signal line 3005. The storage capacitor is
formed between the capacitor electrode 3006 and the capacitor line
3002. An interlayer insulating film 3092 is formed over the source
signal line 3004, the drain signal line 3005, and the capacitor
electrode 3006.
[0205] A plurality of contact holes are provided in the interlayer
insulating film 3092. A reflection electrode 3013 can have
unevenness by using the contact holes. The reflection electrode
3013 and a connection electrode 3012 are formed over the interlayer
insulating film 3092 having the contact holes.
[0206] A cell gap adjusting film 3010 is formed over the reflection
electrode 3013 and the connection electrode 3012. Note that the
cell gap adjusting film 3010 is eliminated at least from the
transmission region. The cell gap adjusting film 3010 may be
eliminated from a region other than the reflection region. A
transparent electrode 3011 is formed over the cell gap adjusting
film 3010. In order to be electrically connected to the transparent
electrode 3011, a part of the reflection electrode 3013 is formed
outside of the cell gap adjusting film 3010, at which it is
connected to the transparent electrode 3011.
[0207] As the electrode of the storage capacitor, the transparent
electrode 3011 and the reflection electrode 3013 may be employed
instead of the capacitor electrode 3006. At that time, a thick
material is preferably eliminated because an insulating film
between the electrodes is preferably as thin as possible in order
to make a capacitance value large.
[0208] In FIG. 30, although the reflection electrode 3013 is
provided, it is not limited to this. The reflection electrode may
be formed by sharing the drain electrode 3005, an electrode or a
wire in the same layer thereof, the capacitor line 3002, or an
electrode or a wire in the same layer thereof, or by forming a new
electrode.
[0209] Next, in the case where the reflection electrode with
unevenness is formed over the cell gap adjusting film as shown in
FIGS. 7A and 7B, FIG. 31 shows an example of a cross sectional view
in the case of employing the bottom gate transistor.
[0210] A gate signal line 3101 and a capacitor line 3102 are formed
of the same material in the same layer. A part of the gate signal
line 3101 functions as a gate electrode of the transistor. A part
of the capacitor line 3102 functions as an electrode of the storage
capacitor A gate insulating film 3191 is formed thereover. Silicon
3103 is formed over the gate insulating film 3191. This portion
functions as the transistor.
[0211] A source signal line 3104 and a drain signal line 3105 are
formed over the silicon 3103. A capacitor electrode 3106 is formed
of the same material in the same layer as the source signal line
3104 and the drain signal line 3105. The storage capacitor is
formed between the capacitor electrode 3106 and the capacitor line
3102. An interlayer insulating film 3192 is formed over the source
signal line 3104, the drain signal line 3105, and the capacitor
electrode 3106, over which a cell gap adjusting film 3110 is
formed. Note that the cell gap adjusting film 3110 is eliminated at
least from the transmission region. Note that the cell gap
adjusting film 3110 may be eliminated from a region other than the
reflection region.
[0212] A transparent electrode 3011 is formed over the cell gap
adjusting film 3110. The transparent electrode 3011 is formed in
the reflection region in order to be electrically connected to a
reflection electrode 3112. A projection portion 3193 is formed
thereover. Note that the projection portion 3193 may be formed
below the transparent electrode 3011. The reflection electrode 3112
is formed subsequently.
[0213] A transparent electrode 3011 is provided below a reflection
electrode 3112, thereby being electrically connected to the
reflection electrode 3112.
[0214] As the electrode of the storage capacitor, the transparent
electrode 3011 and the reflection electrode 3112 may be employed
instead of the capacitor electrode 3106. At that time, a thick
material is preferably eliminated because an insulating film
between the electrodes is preferably as thin as possible in order
to make a capacitance value large.
[0215] In FIG. 31, although the reflection electrode 3112 is formed
over the transparent electrode 3011, it is not limited to this. The
transparent electrode 3011 may be formed over the reflection
electrode 3112.
[0216] Although the interlayer insulating film 3192 is formed over
the source signal line 3104, the drain signal line 3105, and the
capacitor electrode 3106, it is not limited to this. If
circumstances require, the interlayer insulating film 3192 is
provided.
[0217] Note that in this embodiment mode, although description is
made of a channel etch type transistor as the bottom gate
transistor, it is not limited to this. A channel protective type
(channel stop type) transistor of which a protective film is formed
at an upper portion of a channel may be employed.
[0218] Next, FIG. 32 shows an example of a cross sectional view in
the case of employing the top gate transistor.
[0219] Silicon 3203 is provided, over which a gate insulating film
3291 is formed. A gate signal line 3201 and a capacitor line 3202
are formed of the same material in the same layer over the gate
insulating film 3291. A part of the gate signal line 3201 provided
over the silicon 3203 functions as a gate electrode of the
transistor. A part of the capacitor line 3202 functions as an
electrode of the storage capacitor. An interlayer insulating film
3292 is formed thereover. A source signal line 3204, a drain signal
line 3205, and a capacitor electrode 3206 are formed of the same
material in the same layer over the interlayer insulating film
3292. The storage capacitor is formed between the capacitor
electrode 3206 and the capacitor line 3202. Note that as the
electrode of the storage capacitor, an electrode in the same layer
as the silicon 3203 may be used, and the storage capacitor may be
formed between the electrode and the capacitor line 3202. A cell
gap adjusting film 3210 is formed thereover. Note that the cell gap
adjusting film 3210 is eliminated at least from the transmission
region. The cell gap adjusting film 3210 may be eliminated from a
region other than the reflection region.
[0220] A transparent electrode 3211 is formed over the cell gap
adjusting film 3210. The transparent electrode 3211 is formed in
the reflection region in order to be electrically connected to a
reflection electrode 3213. The reflection electrode 3213 is formed
over the transparent electrode 3211.
[0221] The transparent electrode 3211 is provided below the
reflection electrode 3213, thereby being electrically connected to
the reflection electrode 3113.
[0222] As the electrode of the storage capacitor, the transparent
electrode 3211 and the reflection electrode 3213 may be employed
instead of the capacitor electrode 3206. At that time, a thick
material is preferably eliminated because an insulating film
between the electrodes is preferably as thin as possible in order
to make a capacitance value large.
[0223] Note that in FIG. 32, although the reflection electrode 3213
is formed over the transparent electrode 3211, it is not limited to
this. The transparent electrode 3211 may be formed over the
reflection electrode 3213.
[0224] Next, in the case where the reflection electrode with
unevenness is formed below the cell gap adjusting film as shown in
FIGS. 9A and 9B, FIG. 33 shows an example of a cross sectional view
in the case of employing the top gate transistor.
[0225] Silicon 3303 is provided, over which a gate insulating film
3391 is formed. A gate signal line 3301 and a capacitor line 3302
are formed of the same material in the same layer over the gate
insulating film 3391. A part of the gate signal line 3301, which is
provided over the silicon 3303, functions as a gate electrode of
the transistor. A part of the capacitor line 3302 functions as an
electrode of the storage capacitor. An interlayer insulating film
3392 is formed thereover. A source signal line 3304, a drain signal
line 3305, and a capacitor electrode 3306 are formed of the same
material in the same layer over the gate insulating film 3392. The
storage capacitor is formed between the capacitor electrode 3306
and the capacitor line 3302. Note that as the electrode of the
storage capacitor, an electrode in the same layer as the silicon
2203 may be used, and the storage capacitor may be formed between
the electrode and the capacitor line 3302.
[0226] An interlayer insulating film 3393 is formed over the source
signal line 3304, the drain signal line 3305, the capacitor
electrode 3306, and the like. A plurality of contact holes are
provided in the interlayer insulating film 3393. A reflection
electrode 3313 can have unevenness by using the contact holes. The
reflection electrode 3313 and a connection electrode 3214 are
formed over the interlayer insulating film 3393 having the contact
holes.
[0227] A cell gap adjusting film 3310 is formed over the reflection
electrode 3213 and the connection electrode 3314. Note that the
cell gap adjusting film 3310 is eliminated at least from the
transmission region. The cell gap adjusting film 3310 may be
eliminated from a region other than the reflection region.
[0228] A transparent electrode 3311 is formed over the cell gap
adjusting film 3310. In order to be electrically connected to the
transparent electrode 3311, a part of the reflection electrode 3313
is formed outside of the cell gap adjusting film 3310, at which it
is connected to the transparent electrode 3311.
[0229] Note that as the electrode of the storage capacitor, the
transparent electrode 3311 and the reflection electrode 3313 may be
employed instead of the capacitor electrode 3306. At that time, a
thick material is preferably eliminated because an insulating film
between the electrodes is preferably as thin as possible in order
to make a capacitance value large.
[0230] Note that in FIG. 33, although the reflection electrode 3313
is provided, it is not limited to this. The reflection electrode
may be formed by sharing the drain electrode 3305, an electrode or
a wire in the same layer thereof, the capacitor line 3302, or an
electrode or a wire in the same layer thereof, or by forming a new
electrode.
[0231] In this invention, various kinds of transistors can be
applied such as a thin film transistor (TFT) using a
non-monocrystalline semiconductor film typified by amorphous
silicon or polycrystalline silicon, a MOS transistor which is
formed by using a semiconductor substrate or an SOI substrate, a
junction type transistor, a bipolar transistor, a transistor using
an organic semiconductor or a carbon nanotube, or other
transistors. In addition, a substrate over which a transistor is
provided is not limited, and a monocrystalline substrate, an SOI
substrate, a grass substrate, or the like can be employed.
[0232] Note that the thin film transistor is preferably used for a
transistor which is employed in this invention. As using the thin
film transistor, a grass substrate, which is inexpensive and
transparent, can be used as a substrate.
[0233] Note that in the specification, a semiconductor device is a
device including a circuit which has a semiconductor element (a
transistor, a diode, or the like). A light emitting device is a
device including a circuit which has a light emitting element (an
organic EL element, an element used for FED, or the like). A
display device is a device including a circuit which has a display
element (an organic EL element, a liquid crystal element, a DMD, or
the like).
[0234] Note that cross-sectional structures described in this
specification are only examples, and it is not limited to these.
Various structures can be obtained by combining the description in
Embodiment modes 1 to 8 freely. Description in this embodiment mode
is a part of these combinations, and further, various combinations
can be realized.
Embodiment Mode 10
[0235] A substrate over which the cell gap adjusting film is formed
and an opposite substrate between which the liquid crystal is
sandwiched are required to be maintained with a certain cell gap.
Therefore, a spacer is required to be provided.
[0236] In that case, a method by which spacers of bead shape
(spherical shape) are spread over a whole substrate and the liquid
crystal is injected is used in general. However, in the case of the
semi-transmission type liquid crystal including the vertically
aligned liquid crystal in the invention, the spacers of bead shape
(spherical shape) cannot maintain a cell gap well because cell gaps
are different in the transmission region and in the reflection
region.
[0237] Therefore, as shown in FIGS. 34 and 35, a spacer 3401 and a
spacer 3501 are preferably formed over the cell gap adjusting film
103 or a film which is formed of the same layer as the cell gap
adjusting film 103. In that case, the spacer 3401 and the spacer
3501 contribute to inclining the liquid crystal molecules in a
specific direction. Therefore, a slit (a gap, a space, or the like)
of an electrode and the projection 1905a are preferably not
provided near the spacer 3401 and the spacer 3501.
[0238] The spacer 3401 and the spacer 3501 are required to be thick
films; therefore, preferably formed of a material containing an
organic material. The material containing an organic material
preferably includes acrylic, polyimide, polycarbonate, or the like,
for example. In addition, the spacer may be formed of a material
similarly to the cell gap adjusting film or by using a color filter
or the like. That is, layers of each color which are used for a
color filter or a protrusion are stacked appropriately to function
as a spacer.
[0239] By such the spacer 3401 and the spacer 3501, a certain cell
gap between the substrate over which the cell gap adjusting film is
formed and the opposite substrate can be maintained. Note that in
FIGS. 34 and 35, the transparent electrodes 1601 and 1701 are
formed over the opposite substrate, respectively.
[0240] In addition, the spacer 3401 and the spacer 3501, which are
provided other than minimum necessary spacers to maintain a cell
gap, may be higher or lower than the spacers, which maintain the
cell gap.
[0241] A liquid crystal material in the invention is not limited to
the vertically aligned liquid crystal. A horizontally aligned
liquid crystal, a TN liquid crystal, an IPS liquid crystal, or a
ferroelectric liquid crystal may be employed.
[0242] Note that description in this embodiment mode can commonly
used for the description in Embodiment Modes 1 to 9. Therefore, the
description in Embodiment Modes 1 to 9 can be combined with the
description in this embodiment mode.
Embodiment Mode 11
[0243] In this embodiment mode, description is made of a method for
manufacturing a semiconductor device by using plasma treatment as
for a method for manufacturing a semiconductor device including a
transistor.
[0244] FIGS. 36A to 36C show views of a structural example of a
semiconductor device including a transistor. Note that FIG. 36B
corresponds to a cross sectional view taken a line a-b in FIG. 36A,
and FIG. 36C corresponds to a cross-sectional view taken a line c-d
in FIG. 36A.
[0245] A semiconductor device shown in FIG. 36A to 36C includes a
semiconductor film 4603a and a semiconductor film 4603b which are
formed over a substrate 4601 with an insulating film 4602
sandwiched therebetween, a gate electrode 4605 which is formed over
the semiconductor film 4603a and the semiconductor film 4603b with
an gate insulating film 4604 sandwiched therebetween, an insulating
film 4606 and an insulating film 4607 which are formed to cover the
gate electrode, a conductive film 4608 which is electrically
connected to a source region or a drain region of the semiconductor
film 4603a and the semiconductor film 4603b and formed over the
insulating film 4607. Note that although FIGS. 36A to 36C show the
case where an n-channel transistor 4610a which uses a part of the
semiconductor film 4603a as a channel region and a p-channel
transistor 4610b which uses a part of the semiconductor film 4603b
as a channel region are provided, a structure is not limited to
this. For example, in FIGS. 36A to 36C, although an LDD region is
provided in the n-channel transistor 4610a and is not provided in
the p-channel transistor 4610b, a structure in which LDD regions
are provided in both transistors or a structure in which an LDD
region is provided in neither of the transistors can be
applied.
[0246] Note that in this embodiment mode, the semiconductor device
shown in FIGS. 36A to 36C is manufactured by oxidizing or nitriding
at least one layer of the substrate 4601, the insulating film 4602,
the semiconductor film 4603a, the semiconductor film 4603b, the
gate insulating film 4604, the insulating film 4606 and the
insulating film 4607 by plasma treatment so as to oxidize or
nitride a semiconductor film or an insulating film. By oxidizing or
nitriding the semiconductor film or the insulating film by plasma
treatment in such a manner, a surface of the semiconductor film or
the insulating film is modified, and the insulating film can be
formed to be denser than an insulating film formed by a CVD method
or a sputtering method; therefore, a defect such as a pinhole can
be reduced, and characteristics and the like of the semiconductor
device can be improved.
[0247] Note that in this embodiment mode, description id made of a
method for manufacturing a semiconductor device by performing
plasma treatment on the semiconductor films 4603a and 4603b, or the
gate insulating film 4604 in FIGS. 36A to 36C and oxidizing or
nitriding the semiconductor films 4603a and 4603b, or the gate
insulating film 4604, with reference to drawings.
[0248] As for an island-shaped semiconductor film which is formed
over a substrate, description is made of the case where an edge
portion of the island-shaped semiconductor film is provided with a
shape close to a right-angled shape.
[0249] First, the island-shaped semiconductor films 4603a and 4603b
are formed over the substrate 4601 (FIG. 37A). The island-shaped
semiconductor films 4603a and 4603b can be provided by forming an
amorphous semiconductor film, which is formed of a material
including silicon (Si) as a main component (for example,
Si.sub.xGe.sub.1-x, or the like) or the like, by using a sputtering
method, an LPCVD method, a plasma CVD method, or the like over the
insulating film 4602 which is formed in advance over the substrate
4601, by crystallizing the amorphous semiconductor film, and by
etching a part of the semiconductor film. Note that crystallization
of the amorphous semiconductor film can be performed by a
crystallization method such as a laser crystallization method, a
thermal crystallization method using RTA or an annealing furnace, a
thermal crystallization method using a metal element which promotes
crystallization, a method of a combination thereof, or the like.
Note that in FIGS. 37A to 37D, edge portions of the island-shaped
semiconductor films 4603a and 4603b are formed to have an angle of
about 90 degrees (.theta.=85 to 100 degrees). Note that an angle
.theta. denotes an angle of a semiconductor film side, which is
formed by a side face of the island-shaped semiconductor film and
the insulating film 4602.
[0250] Next, oxide films or nitride films 4621a and 4621b
(hereinafter also referred to as an insulating film 4621a and an
insulating film 4621b) are formed on surfaces of the semiconductor
films 4603a and 4603b by oxidizing or nitriding the semiconductor
films 4603a and 4603b by plasma treatment (FIG. 37B). For example,
in the case where Si is used for the semiconductor films 4603a and
4603b, silicon oxide (SiO.sub.x) or silicon nitride (SiN.sub.x) is
formed as the insulating film 4621a and the insulating film 4621b.
In addition, the semiconductor films 4603a and 4603b may be
oxidized by plasma treatment, and then may be nitrided by
performing plasma treatment again. In that case, silicon oxide
(SiO.sub.x) is formed in contact with the semiconductor films 4603a
and 4603b, and silicon nitride oxide (SiN.sub.xO.sub.y) (x>y) is
formed on the surface of the silicon oxide. Note that in the case
where the semiconductor film is oxidized by plasma treatment, the
plasma treatment is performed in an oxygen atmosphere (for example,
in an atmosphere of oxygen (O.sub.2) and at least one of an inert
gas (He, Ne, Ar, Kr, Xe), in an atmosphere of oxygen, hydrogen
(H.sub.2), and an inert gas, or in an atmosphere of dinitrogen
mono-oxide and an inert gas). On the other hand, in the case the
semiconductor film is nitrided by plasma treatment, the plasma
treatment is performed in a nitrogen atmosphere (for example, in an
atmosphere of nitrogen (N.sub.2) and at least one of an inert gas
(He, Ne, Ar, Kr, Xe), in an atmosphere of nitrogen, hydrogen, and
an inert gas, or in an atmosphere of NH.sub.3 and an inert gas). As
an inert gas, Ar may be used, for example. Further, a gas nixed
with Ar and Kr may be used. Therefore, the insulating films 4621a
and 4621b include an inert gas (including as least one of He, Ne,
Ar, Kr, Xe) which is used for plasma treatment. In the case where
Ar is used, the insulating films 4621a and 4621b include Ar.
[0251] In addition, the plasma treatment is performed in the
atmosphere containing the aforementioned gas, with conditions of a
plasma electron density ranging from 1.times.10.sup.11 to
1.times.10.sup.13 cm.sup.-3, and a plasma electron temperature
ranging from 0.5 to 1.5 eV. Since the plasma electron density is
high and the electron temperature in the vicinity of a treatment
subject (here, the semiconductor films 4603a and 4603b) formed over
the substrate 4601 is low, damage by plasma to the treatment
subject can be prevented. In addition, since the plasma electron
density is as high as 1.times.10.sup.11 cm.sup.-3 or more, an oxide
film or a nitride film formed by oxidizing or nitriding the
treatment subject by plasma treatment is superior in its uniformity
of thickness and the like as well as being dense, as compared with
a film formed by a CVD method, a sputtering method, or the like.
Further, since the plasma electron temperature is as low as 1 eV or
less, oxidation or nitridation can be performed at a lower
temperature, compared with a conventional plasma treatment or
thermal oxidation. For example, oxidation or nitridation can be
performed sufficiently even when plasma treatment is performed at a
temperature lower than a strain point of a glass substrate by 100
degrees or more. Note that as a frequency for generating plasma, a
high frequency wave such as a microwave (2.45 GHz) can be used.
Note that the plasma treatment is performed using the
aforementioned conditions unless otherwise specified.
[0252] Next, the gate insulating film 4604 is formed so as to cover
the insulating films 4621a and 4621b (FIG. 37C). The gate
insulating film 4604 can be formed by a sputtering method, an LPCVD
method, a plasma CVD method, or the like, and provided with a
single-layer structure or a stacked-layer structure of an
insulating film including oxygen or nitrogen, such as silicon oxide
(SiO.sub.x), silicon nitride (SiN.sub.x), silicon oxynitride
(SiO.sub.xN.sub.y) (x>y), or silicon nitride oxide
(SiN.sub.xO.sub.y) (x>y). For example, in the case where Si is
used for the semiconductor films 4603a and 4603b, and Si is
oxidized by plasma treatment to form silicon oxide as the
insulating films 4621a and 4621b on the surfaces of the
semiconductor films 4603a and 4603b, silicon oxide (SiO.sub.x) is
formed as the gate insulating film over the insulating films 4621a
and 4621b. In addition, in FIG. 37B, in the case where the
insulating films 4621a and 4621b which are formed by oxidizing or
nitriding the semiconductor films 4603a and 4603b by plasma
treatment are sufficiently thick, the insulating films 4621a and
4621b can be used as gate insulating films.
[0253] Next, by forming the gate electrode 4605 and the like over
the gate insulating film 4604, a semiconductor device including the
n-channel transistor 4610a and the p-channel transistor 4610b which
use the island-shaped semiconductor films 4603a and 4603b as
channel regions can be manufactured (FIG. 37D).
[0254] In this manner, by oxidizing or nitriding the surfaces of
the semiconductor films 4603a and 4603b by plasma treatment before
providing the gate insulating film 4604 over the semiconductor
films 4603a and 4603b, a short circuit between the gate electrode
and the semiconductor films, which may be caused by a coverage
defect of the gate insulating film 4604 at edge portions 4651a and
4651b of the channel regions, or the like can be prevented. That
is, in the case where the edge portions of the island-shaped
semiconductor films have an angle of about 90 degrees (.theta.=85
to 100 degrees), the edges of the semiconductor films might not be
properly covered with a gate insulating film when the gate
insulating film is formed to cover the semiconductor film by a CVD
method, a sputtering method, or the like. However, such a coverage
defect and the like of the gate insulating film at the edges of the
semiconductor films can be prevented by oxidizing or nitriding the
surfaces of the semiconductor films by plasma treatment in
advance.
[0255] In addition, in FIGS. 37A to 37D, the gate insulating film
4604 may be oxidized or nitrided by further performing plasma
treatment after forming the gate insulating film 4604. In this
case, an oxide film or a nitride film 4623 (hereinafter also
referred to as an insulating film 4623) is formed on the surface of
the gate insulating film 4604 (FIG. 38B) by oxidizing or nitriding
the gate insulating film 4604 by performing plasma treatment to the
gate insulating film 4604 which is formed to cover the
semiconductor films 4603a and 4603b (FIG. 38A). The plasma
treatment can be performed under similar conditions to those in
FIG. 37B. In addition, the insulating film 4623 includes an inert
gas which is used for the plasma treatment, and for example,
includes Ar in the case where Ar is used for the plasma
treatment.
[0256] In addition, in FIG. 38B, the gate insulating film 4604 is
oxidized by performing plasma treatment in an oxygen atmosphere
once, and after that, may be nitrided by plasma treatment in a
nitrogen atmosphere. In this case, silicon oxide (SiO.sub.x) or
silicon oxynitride (SiO.sub.xN.sub.y) (x>y) is formed on the
semiconductor films 4603a and 4603b side, and silicon nitride oxide
(SiN.sub.xO.sub.y) (x>y) is formed to be in contact with the
gate electrode 4605. Subsequently, by forming the gate electrode
4605 and the like over the insulating film 4623, a semiconductor
device having the n-channel transistor 4610a and the p-channel
transistor 4610b which have the island-shaped semiconductor films
4603a and 4603b as channel regions can be manufactured (FIG. 38C).
In this manner, by oxidizing or nitriding the surface of the gate
insulating film by plasma treatment, the surface of the gate
insulating film can be modified to form a dense film. The
insulating film obtained by plasma treatment is denser and has
fewer defects such as a pinhole as compared with an insulating film
formed by a CVD method or a sputtering method. Therefore, the
characteristics of the transistors can be improved.
[0257] Note that although FIG. 38A to 38C show the case where the
surfaces of the semiconductor films 4603a and 4603b are oxidized or
nitrided by performing plasma treatment to the semiconductor films
4603a and 4603b in advance, a method where plasma treatment is
performed after forming the gate insulating film 4604 without
performing to the semiconductor films 4603a and 4603b may be
employed. In this manner, by performing plasma treatment before
forming the gate electrode, an exposed portion of the semiconductor
film due to a coverage defect can be oxidized or nitrided even if a
coverage defect such as breaking of a gate insulating film is
caused at edge portions of the semiconductor film; therefore, a
short circuit between the gate electrode and the semiconductor
film, which is caused by a coverage defect of the gate insulating
film at the edges of the semiconductor film, or the like can be
prevented.
[0258] In this manner, even in the case where the island-shaped
semiconductor films are formed to have edges with an angle of about
90 degrees, a short circuit between the gate electrodes and the
semiconductor films, which is caused by a coverage defect of the
gate insulating film at the edges of the semiconductor films, or
the like can be prevented by oxidizing or nitriding the
semiconductor films or the gate insulating film by plasma
treatment.
[0259] Next, as for the island-shaped semiconductor films formed
over the substrate, FIGS. 39A to 39D show the case where the edge
portions of the island-shaped semiconductor films are provided with
a tapered shape (.theta.=30 to 85 degrees).
[0260] First, the island-shaped semiconductor films 4603a and 4603b
are formed over the substrate 4601 (FIG. 39A). The island-shaped
semiconductor films 4603a and 4603b can be provided by forming an
amorphous semiconductor film, which is formed of a material
including silicon (Si) as a main component (for example,
Si.sub.xGe.sub.1-x, or the like) and the like, by using a
sputtering method, an LPCVD method, a plasma CVD method, or the
like over the insulating film 4602 which is formed in advance over
the substrate 4601, by crystallizing the amorphous semiconductor
film by a crystallization method such as a laser crystallization
method, a thermal crystallization method using RTA or an annealing
furnace, a thermal crystallization method using a metal element
which promotes crystallization, or a method of a combination
thereof, and by etching and removing a part of the semiconductor
film. Note that in FIGS. 39A to 39D, the edge portions of the
island-shaped semiconductor films 4603a and 4603b are provided to
have a tapered shape (.theta.=30 to 85 degrees).
[0261] Next, the gate insulating film 4604 is formed so as to cover
the semiconductor films 4603a and 4603b (FIG. 39B). The gate
insulating film 4604 can be provided to have a single-layer
structure or a stacked-layer structure of an insulating film
containing oxygen or nitrogen, such as silicon oxide (SiO.sub.x),
silicon nitride (SiN.sub.x), silicon oxynitride (SiO.sub.xN.sub.y)
(x>y), or silicon nitride oxide (SiN.sub.xO.sub.y) (x>y) by a
sputtering method, an LPCVD method, a plasma CVD method, or the
like.
[0262] Next, an oxide film or a nitride film 4624 (hereinafter also
referred to as an insulating film 4624) is formed on the surface of
the gate insulating film 4604 by oxidizing or nitriding the gate
insulating film 4604 by plasma treatment (FIG. 39C). The plasma
treatment can be performed under similar conditions to the
aforementioned description. For example, in the case where silicon
oxide (SiO.sub.x) or silicon oxynitride (SiO.sub.xN.sub.y) (x>y)
is used as the gate insulating film 4604, the gate insulating film
4604 is oxidized by performing plasma treatment in an oxygen
atmosphere, thereby a dense insulating film with few defects such
as a pinhole can be formed on the surface of the gate insulating
film in comparison with a gate insulating film formed by a CVD
method, a sputtering method, or the like. On the other hand, if the
gate insulating film 4604 is nitrided by plasma treatment in a
nitrogen atmosphere, silicon nitride oxide (SiN.sub.xO.sub.y)
(x>y) can be provided as the insulating film 4624 on the surface
of the gate insulating film 4604. Further, the gate insulating film
4604 is oxidized by performing plasma treatment in an oxygen
atmosphere once, and after that, may be nitrided by plasma
treatment in a nitrogen atmosphere. In addition, the insulating
film 4624 includes an inert gas which is used for the plasma
treatment, and for example, includes Ar in the case where Ar is
used.
[0263] Next, by forming the gate electrode 4605 and the like over
the gate insulating film 4604, a semiconductor device including the
n-channel transistor 4610a and the p-channel transistor 4610b which
use the island-shaped semiconductor films 4603a and 4603b as
channel regions can be manufactured (FIG. 39D).
[0264] In this manner, by performing plasma treatment to the gate
insulating film, the insulating film formed of an oxide film or a
nitride film can be provided on the surface of the gate insulating
film, and the surface of the gate insulating film can be modified.
The insulating film obtained by oxidation or nitridation with
plasma treatment is denser and has fewer defects such as a pinhole
as compared with a gate insulating film formed by a CVD method or a
sputtering method; therefore, the characteristics of the
transistors can be improved In addition, while a short circuit
between the gate electrodes and the semiconductor films, which is
caused by a coverage defect of the gate insulating film at the
edges of the semiconductor films, or the like can be suppressed by
forming the semiconductor films to have a tapered shape, a short
circuit or the like between the gate electrodes and the
semiconductor films can be prevented even more effectively by
performing plasma treatment after forming the gate insulating
film.
[0265] Next, description is made of a manufacturing method of a
semiconductor device which is different from that in FIGS. 39A to
39D with reference to FIGS. 40A to 40D. Specifically, a case is
shown where plasma treatment is selectively performed to
semiconductor films having a tapered shape.
[0266] First, the island-shaped semiconductor films 4603a and 4603b
are formed over the substrate 4601 (FIG. 40A). The island-shaped
semiconductor films 4603a and 4603b can be provided by forming an
amorphous semiconductor film over the insulating film 4602 which is
formed over the substrate 4601 in advance, by a sputtering method,
an LPCVD method, a plasma CVD method, or the like, using a material
containing silicon (Si) as a main component (e.g.,
Si.sub.xGe.sub.1-x) or the like, crystallizing the amorphous
semiconductor film and providing resists 4625a and 4625b used as
masks for etching the semiconductor film selectively. Note that
crystallization of the amorphous semiconductor film can be
performed by a laser crystallization method, a thermal
crystallization method using RTA or an annealing furnace, a thermal
crystallization method using metal elements which promote
crystallization, or a combination of these methods.
[0267] The edge portions of the island-shaped semiconductor films
4603a and 4603b are selectively oxidized or nitrided by plasma
treatment before removing the resists 4625a and 4625b which are
used for etching the semiconductor films, thereby an oxide film or
a nitride film 4626 (hereinafter also referred to as an insulating
film 4626) is formed on each edge portion of the semiconductor
films 4603a and 4603b (FIG. 40B). The plasma treatment is performed
under the aforementioned conditions. In addition, the insulating
film 4626 contains an inert gas which is used for the plasma
treatment.
[0268] The gate insulating film 4604 is formed to cover the
semiconductor films 4603a and 4603b after the resist 4625a and
4625b are removed (FIG. 40C). The gate insulating film 4604 can be
formed in a similar manner to the above description.
[0269] By forming the gate electrodes 4605 and the like over the
gate insulating film 4604, a semiconductor device having the
n-channel transistor 4610a and the p-channel transistor 4610b which
have the island-shaped semiconductor films 4603a and 4603b as
channel regions can be manufactured (FIG. 40D).
[0270] When the edge portions of the semiconductor films 4603a and
4603b have tapered shapes, edge portions 4652a and 4652b of the
channel regions which are formed in a part of the semiconductor
films 4603a and 4603b are also tapered, thereby the thickness of
the semiconductor films and the gate insulating film in that
portion are different from that in a central portion, which may
adversely affect the characteristics of the transistors. However,
such an effect on the transistors due to the edge portions of the
channel regions can be reduced by forming insulating films on the
edge portions of the semiconductor films, which are formed by
selectively oxidizing or nitriding the edge portions of the channel
regions by plasma treatment here.
[0271] Although FIGS. 40A to 40D show an example where only the
edge portions of the semiconductor films 4603a and 4603b are
oxidized or nitrided by plasma treatment, the gate insulating film
4604 can also be oxidized or nitrided by plasma treatment as shown
in FIGS. 39A to 39D (FIG. 42A).
[0272] Next, description is made of a manufacturing method of a
semiconductor device which is different from the aforementioned
manufacturing method with reference to FIGS. 41A to 41D.
Specifically, a case is shown where plasma treatment is performed
to semiconductor films with tapered shapes.
[0273] First, the island-shaped semiconductor films 4603a and 4603b
are formed over the substrate 4601 in a similar manner to the above
description (FIG. 41A).
[0274] The semiconductor films 4603a and 4603b are oxidized or
nitrided by plasma treatment, thereby forming oxide films or
nitride films (hereinafter also referred to as insulating films
4627a and 4627b) on the surfaces of the semiconductor films 4603a
and 4603b respectively (FIG. 41B). The plasma treatment can be
similarly performed under the aforementioned conditions. For
example, when Si is used for the semiconductor films 4603a and
4603b, silicon oxide (SiO.sub.x) or silicon nitride (SiN.sub.x) is
formed as the insulating films 4627a and 4627b. In addition, after
oxidizing the semiconductor films 4603a and 4603b by plasma
treatment, plasma treatment may be performed again to the
semiconductor films 4603a and 4603b, so as to be nitrided. In this
case, silicon oxide (SiO.sub.x) or silicon oxynitride
(SiO.sub.xN.sub.y) (x>y) is formed on the semiconductor films
4603a and 4603b, and silicon nitride oxide (SiN.sub.xO.sub.y)
(x>y) is formed on the surface of the silicon oxide. Therefore,
the insulating films 4627a and 4627b contain an inert gas which is
used for the plasma treatment. Note that the edge portions of the
semiconductor films 4603a and 4603b are simultaneously oxidized or
nitrided by performing plasma treatment.
[0275] The gate insulating film 4604 is formed to cover the
insulating films 4627a and 4627b (FIG. 41C). The gate insulating
film 4604 can be formed to have a single-layer structure or a
stacked-layer structure of an insulating film containing oxygen or
nitrogen, such as silicon oxide (SiO.sub.x), silicon nitride
(SiN.sub.x), silicon oxynitride (SiO.sub.xN.sub.y) (x>y), or
silicon nitride oxide (SiN.sub.xO.sub.y) (x>y) by a sputtering
method, an LPCVD method, a plasma CVD method, or the like. For
example, when Si is used for the semiconductor films 4603a and
4603b, and the surfaces of the semiconductor films 4603a and 4603b
are oxidized by plasma treatment to form silicon oxide as the
insulating films 4627a and 4627b, silicon oxide (SiO.sub.x) is
formed as a gate insulating film over the insulating films 4627a
and 4627b.
[0276] By forming the gate electrodes 4605 and the like over the
gate insulating film 4604, a semiconductor device having the
n-channel transistor 4610a and the p-channel transistor 4610b which
have the island-shaped semiconductor films 4603a and 4603b as
channel regions can be manufactured (FIG. 41D).
[0277] When the edge portions of the semiconductor films have
tapered shape, edge portions 4653a and 4653b of the channel regions
which are formed in a part of the semiconductor films are also
tapered, which may adversely affect the characteristics of the
semiconductor elements. The semiconductor films are oxidized or
nitrided by plasma treatment, and accordingly the edge portions of
the channel regions are also oxidized or nitrided; therefore, such
an effect on the semiconductor elements can be reduced.
[0278] Although FIGS. 41A to 41D show an example where only the
semiconductor films 4603a and 4603b are oxidized or nitrided by
plasma treatment, it is needless to say that the gate insulating
film 4604 can be oxidized or nitrided by plasma treatment as shown
in FIGS. 39A to 39D (FIG. 42B). In this case, after oxidizing the
gate insulating film 4604 by plasma treatment under an oxygen
atmosphere, plasma treatment may be performed again to the gate
insulating film 4604 so as to be nitrided. In such a case, silicon
oxide (SiO.sub.x) or silicon oxynitride (SiO.sub.xN.sub.y) (x>y)
is formed on the semiconductor films 4603a and 4603b, and silicon
nitride oxide (SiN.sub.xO.sub.y) (x>y) is formed to be in
contact with the gate electrodes 4605.
[0279] In addition, by performing plasma treatment in the
aforementioned manner, impurities such as dust attached to the
semiconductor film and the insulating film can be easily removed.
In general, dust (also referred to as a particle) is sometimes
attached to the film formed by a CVD method, a sputtering method,
or the like. For example, as shown in FIG. 43A, dust 4673 is
sometimes formed over an insulating film 4672 formed by a CVD
method, a sputtering method, or the like, which is formed over a
film 4671 such as an insulating film, a conductive film, or a
semiconductor film. Even in such a case, the insulating film 4672
is oxidized or nitrided by the plasma treatment and an oxide film
or a nitride film 4674 (hereinafter also referred to as an
insulating film 4674) is formed over the surface of the insulating
film 4672. As for the insulating film 4674, a portion under the
dust 4673 as well as a portion in which the dust 4673 does not
exist is oxidized or nitrided, and thus the volume of the
insulating film 4674 is increased. The surface of the dust 4673 is
also oxidized or nitrided by the plasma treatment to form an
insulating film 4675, and as a result, the volume of the dust 4673
is also increased (FIG. 43B).
[0280] At this time, the dust 4673 can be easily removed from the
surface of the insulating film 4674 by simple cleaning such as
brush cleaning. In this manner, by performing plasma treatment,
even minute dust attached to the insulating film or a semiconductor
film can be removed easily. Note that this effect is obtained by
performing plasma treatment, and can be applied to other embodiment
modes as well as this embodiment mode.
[0281] As described above, by modifying the surface of the
semiconductor film or the gate insulating film by oxidizing or
nitriding by plasma treatment, a dense insulating film with good
film quality can be formed. In addition, dust and the like attached
to the surface of the insulating film can be removed easily by
cleaning. Consequently, even when the insulating film is formed to
be thinner, a defect such as a pinhole can be avoided, and
miniaturization and higher performance of a semiconductor element
such as a transistor can be realized.
[0282] Although this embodiment mode shows an example where plasma
treatment is performed to the semiconductor films 4603a and 4603b,
or the gate insulating film 4604 shown in FIGS. 36A to 36C so as to
oxidize or nitride the semiconductor films 4603a and 4603b, or the
gate insulating film 4604, a layer to be oxidized or nitrided by
plasma treatment is not limited to these. For example, plasma
treatment may be performed to the substrate 4601 or the insulating
film 4602, or to the insulating film 4606 or the insulating film
4607.
[0283] Note that description in this embodiment can be implemented
freely in combination with those in Embodiment Modes 1 to 10.
Embodiment Mode 12
[0284] In this embodiment mode, description is made of a pixel
structure included in a display device with reference to FIGS. 49A
to 49F. Each of pixels shown in FIGS. 49A to 49F includes a
transistor 490, a liquid crystal element 491, and a storage
capacitor 492. A first electrode (one of a source electrode and a
drain electrode) of the transistor 490 is connected to a source
signal line 500. A second electrode (the other of the source
electrode and the drain electrode) thereof is connected to a pixel
electrode of the liquid crystal element 491 and a first electrode
of the storage capacitor 492. A gate electrode of the transistor
490 is connected to a gate line 501. A second electrode of the
storage capacitor 492 is connected to a capacitor line 502. Note
that the liquid crystal element includes the pixel electrode, a
liquid crystal layer, an opposite electrode 493 and a cell gap
adjusting film.
[0285] An analog voltage signal (video signal) is supplied to the
source signal line 500. Note that the video signal may be a digital
voltage signal or a current signal.
[0286] An H-level or L-level voltage signal (video signal) is
supplied to the gate line 501. Note that in the case of using an
n-channel transistor as the transistor 490, the H level voltage
signal is a voltage which can turn on the transistor 490, and the L
level voltage signal is a voltage which can turn off the transistor
490. On the other hand, in the case of using a p-channel transistor
as the transistor 490, the L level voltage signal is a voltage
which can turn on the transistor 490, and the H level voltage
signal is a voltage which can turn off the transistor 490.
[0287] Note that a certain power supply voltage is applied to the
capacitor line 502. Note that a pulsing signal may be supplied to
the capacitor line 502.
[0288] Description is made of an operation of a pixel in FIG. 49A.
Here, description is made of the case using an n-channel transistor
as the transistor 490. First, when the gate line 501 becomes H
level, the transistor 490 is turned on, and the video signal is
supplied to a first electrode of the liquid crystal element 491 and
the first electrode of the storage capacitor 492 from the source
signal line 500 thorough the transistor 490 which is in an on
state. A potential difference between a potential of the capacitor
line 502 and a potential of the video signal is held by the storage
capacitor 492.
[0289] Next, when the gate line 501 becomes L level, the transistor
490 is turned off, and the source signal line 500 and the first
electrode of the liquid crystal element 491 and the first electrode
of the storage capacitor 492 are electrically disconnected.
However, the potential difference between the potential of the
capacitor line 502 and the potential of the video signal is held by
the storage capacitor 492; therefore, a potential of the first
electrode of the storage capacitor 492 can be held as similar
potential as the video signal. Therefore, a potential of the first
electrode of the liquid crystal electrode 491 can be held to be
equal to that of the video signal.
[0290] As described above, luminance can be controlled depending on
transmittance of the liquid crystal element 491 in accordance with
the video signal.
[0291] Note that although not shown in the drawings, the storage
capacitor 492 is not necessarily required if the liquid crystal
element 491 includes a capacitance component enough to hold the
video signal.
[0292] In addition, the liquid crystal element 491 is a
semi-transmission type liquid crystal element including the
reflection region and the transmission region. In the reflection
region and the transmission region, cell gaps are different
depending on a cell gap adjusting film. By using the cell gap
adjusting film, a viewing angle can be increased when displaying an
image and deterioration of image quality due to disorder of
orientation of the liquid crystal can be controlled; therefore, a
semi-transmission type liquid crystal display device with high
display quality can be obtained.
[0293] In addition, as shown in FIG. 49B, one pixel may be formed
by two sub-pixels 511a and 511b. Here, the capacitor line 502 is
commonly used by the sub-pixel 511a and the sub-pixel 511b.
Further, both a liquid crystal element 512 and a liquid crystal
element 513 may be the aforementioned liquid crystal elements 491,
that is, the semi-transmission type liquid crystal elements
including the reflection region and the transmission region, or
either one may be.
[0294] As described above, by dividing one pixel into sub-pixels, a
different voltage can be applied to each sub-pixel. Therefore, area
gray scale display can be performed, and a viewing angle can be
further increased by using a difference of orientation of the
liquid crystal in each sub-pixel.
[0295] In addition, the gate line 501 may be used as a common wire
as shown in FIG. 49C instead of using the capacitor line 502 as a
common wire between sub-pixels as shown in FIG. 49B. Further, the
gate line 501 and the capacitor line 502 may be used as common
wires between the sub-pixels, and the source signal lines 500a and
500b may be provided in each sub-pixel.
[0296] In addition, a structure where a pixel includes two liquid
crystal elements 512 and 513 as shown in FIGS. 49E and 49F instead
of dividing one pixel into a plurality of sub-pixels may be
used.
[0297] Note that description in this embodiment can be implemented
freely in combination with those in Embodiment Modes 1 to 11. In
addition, a pixel structure of a display device of the invention is
not limited to those described above.
Embodiment Mode 13
[0298] FIG. 44 shows a structural example of a portable phone
including a display portion for which a display device of the
invention and the display device using the driving method thereof
are employed.
[0299] A display panel 5410 is detachably incorporated into a
housing 5400. A shape and size of the housing 5400 can be
appropriately changed in accordance with a size of the display
panel 5410. The housing 5400 which fixes the display panel 5410 is
fit into a printed board 5401 and assembled as a module.
[0300] The display panel 5410 is connected to the printed board
5401 through an FPC 5411. A speaker 5402, a microphone 5403, a
transmission/reception circuit 5404, and a signal processing
circuit 5405 including a CPU, a controller and the like are formed
over the printed board 5401. Such a module is combined with an
input unit 5406 and a battery 5407, and stored using a chassis 5409
and a chassis 5412. A pixel portion of the display panel 5410 is
provided so as to be seen from an open window formed in the housing
5412.
[0301] The display panel 5410 may be formed in such a manner that a
pixel portion and a part of peripheral driver circuits (a driver
circuit with a low operating frequency among a plurality of driver
circuits) are formed over a substrate by using TFTs, while another
part of the peripheral driver circuits (a driver circuit with a
high operating frequency among the plurality of driver circuits) is
formed over an IC chip, which may be mounted on the display panel
5410 by COG (Chip On Glass). Alternatively, the IC chip may be
connected to a glass substrate by TAB (Tape Automated Bonding) or
by using a printed board. Note that FIGS. 45A and 45B show examples
of a structure of a display panel, in which a part of peripheral
driver circuits and a pixel portion are formed over a substrate,
while another part of the peripheral driver circuits is formed in
an IC chip to be mounted on the substrate by COG or the like.
[0302] In FIG. 45A, a pixel portion 5302 and peripheral driver
circuits (a first scan line driver circuit 5303 and a second scan
line driver circuit 5304) may be formed over a substrate 5300 of a
display panel, and a signal line driver circuit 5301 may be formed
over the IC chip and mounted on the display panel by COG or the
like. Note that the pixel portion 5302 and the peripheral driver
circuits which are formed integrally over the substrate are sealed
by using a sealing member 5309 to bond a sealing substrate 5308 and
the substrate 5300 together. In addition, IC chips (semiconductor
chips formed of a memory circuit, a buffer circuit, and the like)
5306 and 5307 may be mounted over a connection portion of an FPC
5305 and the display panel by COG or the like. Note that although
only an FPC is shown in the drawings, a printed wiring board (PWB)
may be mounted on the FPC.
[0303] As described above, only a signal line driver circuit, which
is required to operate with high speed, is formed over an IC chip
by using a CMOS or the like; therefore, a reduction in power
consumption can be achieved. In addition, by using a semiconductor
chip such as a silicon wafer as an IC chip, higher-speed operation
and lower power consumption can be achieved. Further, the first
scan line driver circuit 5303 and the second scan line driver
circuit 5304 are formed integrally with the pixel portion 5302, and
thereby cost reduction can be achieved. In addition, an IC chip
formed by a functional circuit (a memory and a buffer) is mounted
on a connection portion of the FPC 5305 and the substrate 5300, and
thereby an area of the substrate can be used effectively.
[0304] In order to further reduce power consumption, all peripheral
driver circuits may be formed over an IC chip, and the IC chip may
be mounted on the display panel by COG or the like. For example, as
shown in FIG. 45B, a pixel portion 5312 may be formed over a
substrate 5310. A signal line driver circuit 5311, a first scan
line driver circuit 5313 and a second scan line driver circuit 5314
may be formed over an IC chip and mounted on the display panel by
COG or the like. Note that an FPC 5315, an IC chip 5316, an IC chip
5317, a sealing substrate 5318, and a sealing member 5319 in FIG.
45B correspond to the FPC 5305, the IC chip 5306, the IC chip 5307,
the sealing substrate 5308, and the sealing member 5309,
respectively.
[0305] By using such a structure, power consumption of the display
device can be reduced, and operation time of a portable phone per
charge can be extended. In addition, cost reduction of a portable
phone can be achieved.
[0306] In addition, by converting an impedance of a signal set to a
scan line or a signal line by a buffer, time for writing a signal
to pixels in one row can be shortened. Therefore, a high-definition
display device can be provided.
[0307] In addition, in order to further reduce power consumption, a
pixel portion is formed over a substrate with TFTs, and all the
peripheral circuits are formed over an IC chip, which may be
mounted on the display panel by COG (Chip On Glass) or the
like.
[0308] By using the display device of the invention, a clear and
high-contrast image can be provided.
[0309] Note that the structure shown in this embodiment mode is an
example of a mobile phone; therefore, the display device of the
invention is not limited to the mobile phone with the
aforementioned structure, and can be applied to mobile phones with
various structures.
[0310] Note that description in this embodiment mode can be
implemented freely in combination with those in Embodiment Modes 1
to 12.
Embodiment Mode 14
[0311] FIG. 46 shows a liquid crystal module combined with a
display panel 5701 and a circuit substrate 5702. The display panel
5701 includes a pixel portion 5703, a scan line driver circuit 5704
and a signal line driver circuit 5705. A control circuit 5706, a
signal dividing circuit 5707, and the like are formed over the
circuit substrate 5702, for example. The display panel 5701 and the
circuit substrate 5702 are connected by a connection wire 5708. An
FPC or the like can be used for the connection wire.
[0312] The order of appearance of subframes and the like are
controlled by mainly the control circuit 5706.
[0313] The display panel 5701 may be formed in such a manner that a
pixel portion and a part of peripheral driver circuits (a driver
circuit with a low operating frequency among a plurality of driver
circuits) are formed over a substrate by using TFTs, while another
part of the peripheral driver circuits (a driver circuit with a
high operating frequency among the plurality of driver circuits) is
formed over an IC chip, which may be mounted on the display panel
5701 by COG (Chip On Glass) or the like. Alternatively, the IC chip
may be mounted on the display panel 5701 by TAB (Tape Automated
Bonding) or by using a printed board. Note that FIG. 45A shows an
example of a structure in which a part of peripheral driver
circuits and a pixel portion are formed over a substrate, while
another part of the peripheral driver circuits is formed in an IC
chip to be mounted on the substrate by COG or the like. By using
such a structure, power consumption of the display device can be
reduced, and operation time of a portable phone per charge can be
extended. In addition, cost reduction of a portable phone can be
achieved.
[0314] In addition, by converting an impedance of a signal set to a
scan line or a signal line by a buffer, time for writing a signal
to pixels in one row can be shortened. Therefore, a high-definition
display device can be provided.
[0315] In addition, in order to further reduce power consumption, a
pixel portion is formed over a glass substrate with TFTs, and all
the signal line driver circuits are formed over an IC chip, which
is mounted on the display panel by COG (Chip On Glass).
[0316] Note that it is preferable that a pixel portion is formed
over a substrate by using TFTs, and all the peripheral driver
circuits are formed over an IC chip, which may be mounted on the
display panel by COG (Chip On Glass). Note that FIG. 45B shows an
example of a structure in which a pixel portion is formed over a
substrate, and an IC chip over which signal line driver circuit is
formed is mounted on the substrate by COG or the like.
[0317] A liquid crystal television receiver can be completed with
the liquid crystal module. FIG. 47 is a block diagram showing a
main structure of the liquid crystal television receiver. A tuner
5801 receives a video signal and an audio signal. The video signal
is processed by a video signal amplifier circuit 5802, a video
signal processing circuit 5803, which converts a signal outputted
from the video signal amplifier circuit 5802 to a color signal
corresponding to each color of red, green and blue, and a control
circuit 5706 which converts the video signal to input
specifications of a driver circuit. The control circuit 5706
outputs signals to each of a scan line side and a signal line side.
When performing digital drive, the signal dividing circuit 5707 may
be provided on the signal line side so that the inputted digital
signal is divided into m signals to be supplied.
[0318] Among the signals received by the tuner 5801, an audio
signal is transmitted to an audio signal amplifier circuit 5804,
and an output thereof is supplied to a speaker 5806 through the
audio signal processing circuit 5805. A control circuit 5807
receives control data on a receiving station (receive frequency)
and volume from an input portion 5808, and transmits the signal to
the tuner 5801 and the audio signal processing circuit 5805.
[0319] A television receiver can be completed by incorporating a
liquid crystal module into a housing. A display portion is formed
by the liquid crystal module. In addition, a speaker, a video input
terminal, and the like are provided appropriately.
[0320] It is needless to say that the invention is not limited to a
television receiver, and can be applied to various uses such as a
monitor of a personal computer, an information display board at a
train station or an airport, and an advertising display board on
the street, specifically as a large-area display medium.
[0321] As described above, by using the display device of the
invention, a clear and high-contrast image can be provided.
[0322] Note that description in this embodiment mode can be
implemented freely in combination with those in Embodiment Modes 1
to 13.
Embodiment Mode 15
[0323] The invention can be applied to various electronic
apparatuses, and specifically to a display portion of an electronic
apparatus. As for such an electronic apparatus, a camera such as a
video camera and a digital camera, a goggle type display, a
navigation system, an audio reproducing device (a car audio, an
audio component stereo, and the like), a computer, a game machine,
a portable information terminal (a mobile computer, a portable
phone, a portable game machine, an electronic book, and the like),
an image reproducing device provided with a recording medium
(specifically, a device for reproducing a recording medium such as
a digital versatile disc (DVD) and having a display for displaying
the reproduced image), and the like are taken for example.
[0324] FIG. 48A shows a display device, which includes a chassis
35001, a supporting base 35002, a display portion 35003, speaker
portions 35004, a video input terminal 35005, and the like. The
display device of the invention can be applied to the display
portion 35003. Note that the display device includes all
information display devices such as those for a personal computer,
TV broadcasting reception, and advertisement display. A display
device which uses the display device of the invention for the
display portion 35003 can provide a clear and high-contrast
image.
[0325] FIG. 48B shows a camera, which includes a main body 35101, a
display portion 35102, an image receiving portion 35103, operating
keys 35104, an external connecting port 35105, a shutter 35106, and
the like.
[0326] A digital camera in which the invention is applied to the
display portion 35102 can be obtained a clear and high-contrast
image.
[0327] FIG. 48C shows a computer, which includes a main body 35201,
a chassis 35202, a display portion 35203, a keyboard 35204, an
external connecting port 35205, a pointing mouse 35206, and the
like. A computer in which the invention is applied to the display
portion 35203 can provide a clear and high-contrast image.
[0328] FIG. 48D shows a mobile computer, which includes a main body
35301, a display portion 35302, a switch 35303, operating keys
35304, an infrared port 35305, and the like. A mobile computer in
which the invention is applied to the display portion 35302 can
provide a clear and high-contrast image.
[0329] FIG. 48E is a portable image reproducing device provided
with a recording medium (specifically, a DVD player), which
includes a main body 35401, a chassis 35402, a display portion A
35403, a display portion B 35404, a recording medium (DVD and the
like) reading portion 35405, an operating key 35406, a speaker
portion 35407, and the like. The display portion A 35403 mainly
displays image data, while the display portion B 35404 mainly
displays text data. An image reproducing device in which the
invention is applied to the display portions A 35403 and B 35404
can provide a clear and high-contrast image can be obtained.
[0330] FIG. 48F shows a goggle type display, which includes a main
body 35501, a display portion 35502, an arm portion 35503, and the
like. A goggle type display in which the invention is applied to
the display portion 35502 can provide a clear and high-contrast
image.
[0331] FIG. 48G shows a video camera, which includes a main body
35601, a display portion 35602, a chassis 35603, an external
connecting port 35604, a remote controller receiving portion 35605,
an image receiving portion 35606, a battery 35607, an audio input
portion 35608, operating keys 35609, and the like. A video camera
in which the invention is applied to the display portion 35602 can
provide a clear and high-contrast image.
[0332] FIG. 48H shows a portable phone, which includes a main body
35701, a chassis 35702, a display portion 35703, an audio input
portion 35704, an audio output portion 35705, an operating key
35706, an external connecting port 35707, an antenna 35708, and the
like. A mobile phone in which the invention is applied to the
display portion 35703 can provide a clear and high-contrast
image.
[0333] As described above, the applicable range of the invention is
so wide that the invention can be applied to electronic apparatuses
of various fields. In addition, the electronic apparatuses in this
embodiment mode may use a display device manufactured with any of
the structures in Embodiment Modes 1 to 14.
[0334] This application is based on Japanese Patent Application
serial No. 2005-303766 filed in Japan Patent Office on Oct. 18,
2005, the entire contents of which are hereby incorporated by
reference.
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